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Oracle® Database
Globalization Support Guide
11g Release 1 (11.1)
B28298-02

September 2007

Oracle Database Globalization Support Guide, 11g Release 1 (11.1)
B28298-02
Copyright © 1996, 2007, Oracle. All rights reserved.
Primary Author:

Cathy Shea

Contributors:
Dan Chiba, Winson Chu, Claire Ho, Gary Hua, Simon Law, Geoff Lee, Peter Linsley,
Qianrong Ma, Keni Matsuda, Meghna Mehta, Valarie Moore, Shige Takeda, Linus Tanaka, Makoto Tozawa,
Barry Trute, Ying Wu, Peter Wallack, Chao Wang, Huaqing Wang, Simon Wong, Michael Yau, Jianping Yang,
Qin Yu, Tim Yu, Weiran Zhang, Yan Zhu
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Contents
Preface ............................................................................................................................................................... xv
Intended Audience....................................................................................................................................
Documentation Accessibility ...................................................................................................................
Related Documentation ............................................................................................................................
Conventions ...............................................................................................................................................

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What's New in Globalization Support? .......................................................................................... xxi
Oracle Database 11g Release 1 (11.1) New Features in Globalization ............................................... xxi
Oracle Database 10g Release 2 (10.2) New Features in Globalization .............................................. xxii

Overview of Globalization Support
Globalization Support Architecture .....................................................................................................
Locale Data on Demand ....................................................................................................................
Architecture to Support Multilingual Applications......................................................................
Using Unicode in a Multilingual Database ....................................................................................
Globalization Support Features ............................................................................................................
Language Support..............................................................................................................................
Territory Support ...............................................................................................................................
Date and Time Formats .....................................................................................................................
Monetary and Numeric Formats .....................................................................................................
Calendar Systems ...............................................................................................................................
Linguistic Sorting ...............................................................................................................................
Character Set Support........................................................................................................................
Character Semantics...........................................................................................................................
Customization of Locale and Calendar Data .................................................................................
Unicode Support ................................................................................................................................

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Choosing a Character Set
Character Set Encoding ...........................................................................................................................
What is an Encoded Character Set? .................................................................................................
Which Characters Are Encoded? .....................................................................................................
Phonetic Writing Systems..........................................................................................................
Ideographic Writing Systems....................................................................................................
Punctuation, Control Characters, Numbers, and Symbols...................................................
Writing Direction ........................................................................................................................

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What Characters Does a Character Set Support? .......................................................................... 2-3
ASCII Encoding........................................................................................................................... 2-4
How are Characters Encoded? ......................................................................................................... 2-6
Single-Byte Encoding Schemes ................................................................................................. 2-7
Multibyte Encoding Schemes.................................................................................................... 2-7
Naming Convention for Oracle Database Character Sets ............................................................ 2-8
Length Semantics ..................................................................................................................................... 2-8
Choosing an Oracle Database Character Set.................................................................................... 2-10
Current and Future Language Requirements............................................................................. 2-11
Client Operating System and Application Compatibility......................................................... 2-11
Character Set Conversion Between Clients and the Server ...................................................... 2-12
Performance Implications of Choosing a Database Character Set........................................... 2-12
Restrictions on Database Character Sets...................................................................................... 2-12
Restrictions on Character Sets Used to Express Names ..................................................... 2-12
Database Character Set Statement of Direction .......................................................................... 2-13
Choosing Unicode as a Database Character Set ......................................................................... 2-13
Choosing a National Character Set............................................................................................... 2-14
Summary of Supported Datatypes ............................................................................................... 2-14
Changing the Character Set After Database Creation.................................................................... 2-15
Monolingual Database Scenario ........................................................................................................ 2-15
Character Set Conversion in a Monolingual Scenario ............................................................... 2-16
Multilingual Database Scenarios....................................................................................................... 2-17
Restricted Multilingual Support ................................................................................................... 2-17
Unrestricted Multilingual Support .............................................................................................. 2-18

Setting Up a Globalization Support Environment
Setting NLS Parameters .......................................................................................................................... 3-1
Choosing a Locale with the NLS_LANG Environment Variable.................................................... 3-3
Specifying the Value of NLS_LANG............................................................................................... 3-5
Overriding Language and Territory Specifications ...................................................................... 3-6
Locale Variants ................................................................................................................................... 3-6
Should the NLS_LANG Setting Match the Database Character Set? ......................................... 3-7
NLS Database Parameters....................................................................................................................... 3-8
NLS Data Dictionary Views.............................................................................................................. 3-8
NLS Dynamic Performance Views .................................................................................................. 3-8
OCINlsGetInfo() Function ................................................................................................................ 3-9
Language and Territory Parameters ...................................................................................................... 3-9
NLS_LANGUAGE ............................................................................................................................. 3-9
NLS_TERRITORY ........................................................................................................................... 3-11
Overriding Default Values for NLS_LANGUAGE and NLS_TERRITORY During a Session
3-13
Date and Time Parameters................................................................................................................... 3-15
Date Formats.................................................................................................................................... 3-15
NLS_DATE_FORMAT ............................................................................................................ 3-15
NLS_DATE_LANGUAGE...................................................................................................... 3-16
Time Formats ................................................................................................................................... 3-17
NLS_TIMESTAMP_FORMAT ............................................................................................... 3-18

NLS_TIMESTAMP_TZ_FORMAT ........................................................................................
Calendar Definitions ............................................................................................................................
Calendar Formats ............................................................................................................................
First Day of the Week ..............................................................................................................
First Calendar Week of the Year ............................................................................................
Number of Days and Months in a Year ................................................................................
First Year of Era........................................................................................................................
NLS_CALENDAR...........................................................................................................................
Numeric and List Parameters..............................................................................................................
Numeric Formats ............................................................................................................................
NLS_NUMERIC_CHARACTERS.................................................................................................
NLS_LIST_SEPARATOR ...............................................................................................................
Monetary Parameters............................................................................................................................
Currency Formats ...........................................................................................................................
NLS_CURRENCY ...........................................................................................................................
NLS_ISO_CURRENCY...................................................................................................................
NLS_DUAL_CURRENCY .............................................................................................................
Oracle Database Support for the Euro .........................................................................................
NLS_MONETARY_CHARACTERS.............................................................................................
NLS_CREDIT ...................................................................................................................................
NLS_DEBIT ......................................................................................................................................
Linguistic Sort Parameters...................................................................................................................
NLS_SORT .......................................................................................................................................
NLS_COMP......................................................................................................................................
Character Set Conversion Parameter .................................................................................................
NLS_NCHAR_CONV_EXCP ........................................................................................................
Length Semantics ..................................................................................................................................
NLS_LENGTH_SEMANTICS .......................................................................................................

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Datetime Datatypes and Time Zone Support
Overview of Datetime and Interval Datatypes and Time Zone Support ...................................... 4-1
Datetime and Interval Datatypes .......................................................................................................... 4-1
Datetime Datatypes ........................................................................................................................... 4-2
DATE Datatype ........................................................................................................................... 4-2
TIMESTAMP Datatype .............................................................................................................. 4-3
TIMESTAMP WITH TIME ZONE Datatype........................................................................... 4-4
TIMESTAMP WITH LOCAL TIME ZONE Datatype............................................................ 4-5
Inserting Values into Datetime Datatypes .............................................................................. 4-5
Choosing a TIMESTAMP Datatype ......................................................................................... 4-8
Interval Datatypes.............................................................................................................................. 4-9
INTERVAL YEAR TO MONTH Datatype .............................................................................. 4-9
INTERVAL DAY TO SECOND Datatype ............................................................................ 4-10
Inserting Values into Interval Datatypes.............................................................................. 4-10
Datetime and Interval Arithmetic and Comparisons..................................................................... 4-10
Datetime and Interval Arithmetic................................................................................................. 4-11
Datetime Comparisons................................................................................................................... 4-11
Explicit Conversion of Datetime Datatypes ................................................................................ 4-11

Datetime SQL Functions......................................................................................................................
Datetime and Time Zone Parameters and Environment Variables .............................................
Datetime Format Parameters.........................................................................................................
Time Zone Environment Variables...............................................................................................
Daylight Saving Time Session Parameter....................................................................................
Choosing a Time Zone File..................................................................................................................
Upgrading the Time Zone File............................................................................................................
DST Transition Rules Changes......................................................................................................
Updating the Time Zone File with the utltzuv2.sql Script........................................................
Setting the Database Time Zone ........................................................................................................
Setting the Session Time Zone ...........................................................................................................
Converting Time Zones With the AT TIME ZONE Clause...........................................................
Support for Daylight Saving Time ....................................................................................................
Examples: The Effect of Daylight Saving Time on Datetime Calculations.............................

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Linguistic Sorting and String Searching
Overview of Oracle Database Sorting Capabilities .......................................................................... 5-1
Using Binary Sorts ................................................................................................................................... 5-2
Using Linguistic Sorts ............................................................................................................................. 5-2
Monolingual Linguistic Sorts ........................................................................................................... 5-2
Multilingual Linguistic Sorts............................................................................................................ 5-3
Multilingual Sorting Levels .............................................................................................................. 5-4
Primary Level Sorts .................................................................................................................... 5-4
Secondary Level Sorts ................................................................................................................ 5-4
Tertiary Level Sorts..................................................................................................................... 5-4
Linguistic Sort Features........................................................................................................................... 5-5
Base Letters ......................................................................................................................................... 5-5
Ignorable Characters.......................................................................................................................... 5-6
Contracting Characters...................................................................................................................... 5-6
Expanding Characters ....................................................................................................................... 5-6
Context-Sensitive Characters............................................................................................................ 5-6
Canonical Equivalence ...................................................................................................................... 5-7
Reverse Secondary Sorting ............................................................................................................... 5-7
Character Rearrangement for Thai and Laotian Characters........................................................ 5-8
Special Letters ..................................................................................................................................... 5-8
Special Combination Letters............................................................................................................. 5-8
Special Uppercase Letters ................................................................................................................. 5-8
Special Lowercase Letters ................................................................................................................. 5-8
Case-Insensitive and Accent-Insensitive Linguistic Sorts ............................................................... 5-9
Examples of Case-Insensitive and Accent-Insensitive Sorts..................................................... 5-10
Specifying a Case-Insensitive or Accent-Insensitive Sort.......................................................... 5-11
Linguistic Sort Examples................................................................................................................ 5-12
Performing Linguistic Comparisons ................................................................................................. 5-13
Linguistic Comparison Examples................................................................................................. 5-15
Using Linguistic Indexes ..................................................................................................................... 5-17
Supported SQL Operations and Functions for Linguistic Indexes.......................................... 5-18
Linguistic Indexes for Multiple Languages................................................................................. 5-18

Requirements for Using Linguistic Indexes ................................................................................ 5-19
Set NLS_SORT Appropriately ............................................................................................... 5-19
Specify NOT NULL in a WHERE Clause If the Column Was Not Declared NOT NULL.......
5-19
Example: Setting Up a French Linguistic Index .................................................................. 5-19
Searching Linguistic Strings ............................................................................................................... 5-20
SQL Regular Expressions in a Multilingual Environment ........................................................... 5-20
Character Range '[x-y]' in Regular Expressions.......................................................................... 5-21
Collation Element Delimiter '[. .]' in Regular Expressions ........................................................ 5-21
Character Class '[: :]' in Regular Expressions .............................................................................. 5-21
Equivalence Class '[= =]' in Regular Expressions....................................................................... 5-22
Examples: Regular Expressions .................................................................................................... 5-22

Supporting Multilingual Databases with Unicode
Overview of Unicode............................................................................................................................... 6-1
What is Unicode?...................................................................................................................................... 6-2
Supplementary Characters ............................................................................................................... 6-2
Unicode Encodings ............................................................................................................................ 6-2
UTF-8 Encoding .......................................................................................................................... 6-2
UCS-2 Encoding .......................................................................................................................... 6-3
UTF-16 Encoding ........................................................................................................................ 6-3
Examples: UTF-16, UTF-8, and UCS-2 Encoding ................................................................... 6-4
Support for Unicode in Oracle Database ........................................................................................ 6-4
Implementing a Unicode Solution in the Database .......................................................................... 6-5
Enabling Multilingual Support with Unicode Databases ............................................................ 6-6
Enabling Multilingual Support with Unicode Datatypes ............................................................ 6-7
How to Choose Between a Unicode Database and a Unicode Datatype Solution ................... 6-8
When Should You Use a Unicode Database? ......................................................................... 6-8
When Should You Use Unicode Datatypes?........................................................................... 6-8
Comparing Unicode Character Sets for Database and Datatype Solutions .............................. 6-9
Unicode Case Studies ........................................................................................................................... 6-11
Designing Database Schemas to Support Multiple Languages................................................... 6-13
Specifying Column Lengths for Multilingual Data.................................................................... 6-13
Storing Data in Multiple Languages ............................................................................................ 6-14
Store Language Information with the Data ......................................................................... 6-14
Select Translated Data Using Fine-Grained Access Control ............................................. 6-14
Storing Documents in Multiple Languages in LOB Datatypes ................................................ 6-15
Creating Indexes for Searching Multilingual Document Contents ......................................... 6-16
Creating Multilexers ................................................................................................................ 6-16
Creating Indexes for Documents Stored in the CLOB Datatype ...................................... 6-17
Creating Indexes for Documents Stored in the BLOB Datatype....................................... 6-17

Programming with Unicode
Overview of Programming with Unicode ........................................................................................... 7-1
Database Access Product Stack and Unicode ................................................................................ 7-1
SQL and PL/SQL Programming with Unicode................................................................................... 7-3

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SQL NCHAR Datatypes.................................................................................................................... 7-4
The NCHAR Datatype ............................................................................................................... 7-4
The NVARCHAR2 Datatype..................................................................................................... 7-4
The NCLOB Datatype ................................................................................................................ 7-5
Implicit Datatype Conversion Between NCHAR and Other Datatypes.................................... 7-5
Exception Handling for Data Loss During Datatype Conversion .............................................. 7-5
Rules for Implicit Datatype Conversion ......................................................................................... 7-6
SQL Functions for Unicode Datatypes............................................................................................ 7-7
Other SQL Functions ......................................................................................................................... 7-8
Unicode String Literals...................................................................................................................... 7-8
NCHAR String Literal Replacement ............................................................................................... 7-9
Using the UTL_FILE Package with NCHAR Data..................................................................... 7-10
OCI Programming with Unicode ....................................................................................................... 7-10
OCIEnvNlsCreate() Function for Unicode Programming ........................................................ 7-10
OCI Unicode Code Conversion..................................................................................................... 7-12
Data Integrity............................................................................................................................ 7-12
OCI Performance Implications When Using Unicode........................................................ 7-12
OCI Unicode Data Expansion ................................................................................................ 7-13
Setting UTF-8 to the NLS_LANG Character Set in OCI ............................................................ 7-14
Binding and Defining SQL CHAR Datatypes in OCI................................................................ 7-14
Binding and Defining SQL NCHAR Datatypes in OCI............................................................. 7-15
Handling SQL NCHAR String Literals in OCI ........................................................................... 7-16
Binding and Defining CLOB and NCLOB Unicode Data in OCI ............................................ 7-17
Pro*C/C++ Programming with Unicode ........................................................................................... 7-17
Pro*C/C++ Data Conversion in Unicode.................................................................................... 7-18
Using the VARCHAR Datatype in Pro*C/C++.......................................................................... 7-18
Using the NVARCHAR Datatype in Pro*C/C++ ...................................................................... 7-19
Using the UVARCHAR Datatype in Pro*C/C++ ...................................................................... 7-19
JDBC Programming with Unicode..................................................................................................... 7-20
Binding and Defining Java Strings to SQL CHAR Datatypes .................................................. 7-20
Binding and Defining Java Strings to SQL NCHAR Datatypes ............................................... 7-21
Using the SQL NCHAR Datatypes Without Changing the Code............................................ 7-22
Using SQL NCHAR String Literals in JDBC ............................................................................... 7-22
Data Conversion in JDBC............................................................................................................... 7-23
Data Conversion for the OCI Driver ..................................................................................... 7-23
Data Conversion for Thin Drivers ......................................................................................... 7-23
Data Conversion for the Server-Side Internal Driver ......................................................... 7-24
Using oracle.sql.CHAR in Oracle Object Types ......................................................................... 7-24
oracle.sql.CHAR....................................................................................................................... 7-24
Accessing SQL CHAR and NCHAR Attributes with oracle.sql.CHAR .......................... 7-26
Restrictions on Accessing SQL CHAR Data with JDBC............................................................ 7-26
Character Integrity Issues in a Multibyte Database Environment ................................... 7-26
ODBC and OLE DB Programming with Unicode........................................................................... 7-27
Unicode-Enabled Drivers in ODBC and OLE DB ...................................................................... 7-27
OCI Dependency in Unicode......................................................................................................... 7-28
ODBC and OLE DB Code Conversion in Unicode..................................................................... 7-28
OLE DB Code Conversions .................................................................................................... 7-29

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ODBC Unicode Datatypes .............................................................................................................
OLE DB Unicode Datatypes ..........................................................................................................
ADO Access .....................................................................................................................................
XML Programming with Unicode......................................................................................................
Writing an XML File in Unicode with Java .................................................................................
Reading an XML File in Unicode with Java ................................................................................
Parsing an XML Stream in Unicode with Java ...........................................................................

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Oracle Globalization Development Kit
Overview of the Oracle Globalization Development Kit ................................................................ 8-1
Designing a Global Internet Application............................................................................................ 8-2
Deploying a Monolingual Internet Application ............................................................................ 8-2
Deploying a Multilingual Internet Application............................................................................. 8-4
Developing a Global Internet Application ......................................................................................... 8-5
Locale Determination ........................................................................................................................ 8-6
Locale Awareness............................................................................................................................... 8-6
Localizing the Content ...................................................................................................................... 8-7
Getting Started with the Globalization Development Kit............................................................... 8-7
GDK Quick Start ...................................................................................................................................... 8-9
Modifying the HelloWorld Application ..................................................................................... 8-10
GDK Application Framework for J2EE............................................................................................. 8-16
Making the GDK Framework Available to J2EE Applications ................................................ 8-18
Integrating Locale Sources into the GDK Framework............................................................... 8-19
Getting the User Locale From the GDK Framework ................................................................. 8-20
Implementing Locale Awareness Using the GDK Localizer .................................................... 8-21
Defining the Supported Application Locales in the GDK......................................................... 8-22
Handling Non-ASCII Input and Output in the GDK Framework .......................................... 8-23
Managing Localized Content in the GDK ................................................................................... 8-25
Managing Localized Content in JSPs and Java Servlets..................................................... 8-25
Managing Localized Content in Static Files......................................................................... 8-26
GDK Java API ........................................................................................................................................ 8-27
Oracle Locale Information in the GDK ........................................................................................ 8-28
Oracle Locale Mapping in the GDK ............................................................................................. 8-28
Oracle Character Set Conversion (JDK 1.4 and Later) in the GDK.......................................... 8-29
Oracle Date, Number, and Monetary Formats in the GDK ...................................................... 8-30
Oracle Binary and Linguistic Sorts in the GDK .......................................................................... 8-31
Oracle Language and Character Set Detection in the GDK ...................................................... 8-32
Oracle Translated Locale and Time Zone Names in the GDK ................................................. 8-33
Using the GDK with E-Mail Programs ........................................................................................ 8-34
The GDK Application Configuration File ....................................................................................... 8-35
locale-charset-maps......................................................................................................................... 8-35
page-charset ..................................................................................................................................... 8-36
application-locales........................................................................................................................... 8-36
locale-determine-rule...................................................................................................................... 8-37
locale-parameter-name................................................................................................................... 8-38
message-bundles ............................................................................................................................. 8-38
url-rewrite-rule ................................................................................................................................ 8-39

Example: GDK Application Configuration File..........................................................................
GDK for Java Supplied Packages and Classes ................................................................................
oracle.i18n.lcsd ................................................................................................................................
oracle.i18n.net ..................................................................................................................................
oracle.i18n.servlet............................................................................................................................
oracle.i18n.text .................................................................................................................................
oracle.i18n.util..................................................................................................................................
GDK for PL/SQL Supplied Packages ................................................................................................
GDK Error Messages ............................................................................................................................

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SQL and PL/SQL Programming in a Global Environment
Locale-Dependent SQL Functions with Optional NLS Parameters............................................... 9-1
Default Values for NLS Parameters in SQL Functions................................................................. 9-2
Specifying NLS Parameters in SQL Functions............................................................................... 9-2
Unacceptable NLS Parameters in SQL Functions ......................................................................... 9-3
Other Locale-Dependent SQL Functions ............................................................................................ 9-4
The CONVERT Function................................................................................................................... 9-4
SQL Functions for Different Length Semantics ............................................................................. 9-5
LIKE Conditions for Different Length Semantics ......................................................................... 9-6
Character Set SQL Functions ............................................................................................................ 9-6
Converting from Character Set Number to Character Set Name ........................................ 9-6
Converting from Character Set Name to Character Set Number ........................................ 9-6
Returning the Length of an NCHAR Column........................................................................ 9-7
The NLSSORT Function .................................................................................................................... 9-7
NLSSORT Syntax ........................................................................................................................ 9-8
Comparing Strings in a WHERE Clause ................................................................................. 9-8
Using the NLS_COMP Parameter to Simplify Comparisons in the WHERE Clause ....... 9-8
Controlling an ORDER BY Clause............................................................................................ 9-9
Miscellaneous Topics for SQL and PL/SQL Programming in a Global Environment ............... 9-9
SQL Date Format Masks ................................................................................................................... 9-9
Calculating Week Numbers........................................................................................................... 9-10
SQL Numeric Format Masks ......................................................................................................... 9-10
Loading External BFILE Data into LOB Columns...................................................................... 9-10

OCI Programming in a Global Environment
Using the OCI NLS Functions ............................................................................................................
Specifying Character Sets in OCI ......................................................................................................
Getting Locale Information in OCI ...................................................................................................
Mapping Locale Information Between Oracle and Other Standards .........................................
Manipulating Strings in OCI..............................................................................................................
Classifying Characters in OCI ............................................................................................................
Converting Character Sets in OCI......................................................................................................
OCI Messaging Functions ...................................................................................................................
lmsgen Utility.........................................................................................................................................

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Character Set Migration
Overview of Character Set Migration ............................................................................................... 11-1
Data Truncation............................................................................................................................... 11-1
Additional Problems Caused by Data Truncation.............................................................. 11-2
Character Set Conversion Issues................................................................................................... 11-3
Replacement Characters that Result from Using the Export and Import Utilities......... 11-3
Invalid Data That Results from Setting the Client's NLS_LANG Parameter Incorrectly ........
11-4
Conversion from Single-byte to Multibyte Character Set and Oracle Data Pump ........ 11-5
Changing the Database Character Set of an Existing Database................................................... 11-6
Migrating Character Data Using a Full Export and Import...................................................... 11-6
Migrating a Character Set Using the CSALTER Script.............................................................. 11-6
Using the CSALTER Script in an Oracle Real Application Clusters Environment ........ 11-7
Migrating Character Data Using the CSALTER Script and Selective Imports ...................... 11-8
Migrating to NCHAR Datatypes........................................................................................................ 11-8
Migrating Version 8 NCHAR Columns to Oracle9i and Later................................................. 11-8
Changing the National Character Set........................................................................................... 11-9
Migrating CHAR Columns to NCHAR Columns ...................................................................... 11-9
Using the ALTER TABLE MODIFY Statement to Change CHAR Columns to NCHAR
Columns 11-9
Using Online Table Redefinition to Migrate a Large Table to Unicode ........................ 11-10
Tasks to Recover Database Schema After Character Set Migration .......................................... 11-11

Character Set Scanner Utilities
The Language and Character Set File Scanner ................................................................................
Syntax of the LCSSCAN Command .............................................................................................
Examples: Using the LCSSCAN Command................................................................................
Getting Command-Line Help for the Language and Character Set File Scanner .................
Supported Languages and Character Sets...................................................................................
LCSSCAN Error Messages.............................................................................................................
The Database Character Set Scanner.................................................................................................
Conversion Tests on Character Data ............................................................................................
Scan Modes in the Database Character Set Scanner ......................................................................
Full Database Scan ..........................................................................................................................
User Scan ..........................................................................................................................................
Table Scan.........................................................................................................................................
Column Scan ....................................................................................................................................
Installing and Starting the Database Character Set Scanner........................................................
Access Privileges for the Database Character Set Scanner........................................................
Installing the Database Character Set Scanner System Tables .................................................
Starting the Database Character Set Scanner ..............................................................................
Creating the Database Character Set Scanner Parameter File ..................................................
Getting Command-Line Help for the Database Character Set Scanner ..................................
Database Character Set Scanner Parameters....................................................................................
Database Character Set Scanner Sessions: Examples...................................................................
Full Database Scan Examples ......................................................................................................

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Database Character Set Scanner Messages.........................................................................
User Scan Examples ......................................................................................................................
Database Character Set Scanner Messages.........................................................................
Single Table Scan Examples.........................................................................................................
Database Character Set Scanner Messages.........................................................................
Database Character Set Scanner Messages.........................................................................
Column Scan Examples................................................................................................................
Database Character Set Scanner Messages.........................................................................
Database Character Set Scanner Reports........................................................................................
Database Scan Summary Report.................................................................................................
Database Size ..........................................................................................................................
Database Scan Parameters ....................................................................................................
Scan Summary ........................................................................................................................
Data Dictionary Conversion Summary ..............................................................................
Application Data Conversion Summary ............................................................................
Application Data Conversion Summary Per Column Size Boundary ...........................
Distribution of Convertible Data Per Table .......................................................................
Distribution of Convertible Data Per Column...................................................................
Indexes To Be Rebuilt ............................................................................................................
Truncation Due To Character Semantics............................................................................
Character Set Detection Result.............................................................................................
Language Detection Result...................................................................................................
Database Scan Individual Exception Report.............................................................................
Database Scan Parameters ....................................................................................................
Data Dictionary Individual Exceptions ..............................................................................
Application Data Individual Exceptions ............................................................................
How to Handle Convertible or Lossy Data in the Data Dictionary ..........................................
Storage and Performance Considerations in the Database Character Set Scanner................
Storage Considerations for the Database Character Set Scanner ...........................................
CSM$TABLES.........................................................................................................................
CSM$COLUMNS ...................................................................................................................
CSM$ERRORS ........................................................................................................................
Performance Considerations for the Database Character Set Scanner..................................
Using Multiple Scan Processes.............................................................................................
Setting the Array Fetch Buffer Size .....................................................................................
Optimizing the QUERY Clause ...........................................................................................
Suppressing Exception and Convertible Log ....................................................................
Recommendations and Restrictions for the Database Character Set Scanner......................
Scanning Database Containing Data Not in the Database Character Set ......................
Scanning Database Containing Data from Two or More Character Sets.......................
Database Character Set Scanner CSALTER Script........................................................................
Checking Phase of the CSALTER Script ...................................................................................
Updating Phase of the CSALTER Script....................................................................................
Database Character Set Scanner Views...........................................................................................
CSMV$COLUMNS .......................................................................................................................
CSMV$CONSTRAINTS ...............................................................................................................
CSMV$ERRORS ............................................................................................................................

xii

12-18
12-19
12-19
12-19
12-20
12-21
12-21
12-21
12-22
12-22
12-23
12-23
12-23
12-24
12-29
12-29
12-29
12-30
12-30
12-30
12-30
12-31
12-31
12-31
12-32
12-32
12-33
12-35
12-35
12-35
12-35
12-36
12-36
12-36
12-36
12-36
12-36
12-37
12-37
12-37
12-37
12-38
12-39
12-39
12-40
12-40
12-41

CSMV$INDEXES........................................................................................................................... 12-41
CSMV$TABLES ............................................................................................................................. 12-41
Database Character Set Scanner Error Messages .......................................................................... 12-42

Customizing Locale Data
Overview of the Oracle Locale Builder Utility................................................................................
Configuring Unicode Fonts for the Oracle Locale Builder .......................................................
Font Configuration on Windows...........................................................................................
Font Configuration on Other Platforms ...............................................................................
The Oracle Locale Builder User Interface ....................................................................................
Oracle Locale Builder Pages and Dialog Boxes ..........................................................................
Existing Definitions Dialog Box.............................................................................................
Session Log Dialog Box ...........................................................................................................
Preview NLT Tab Page ...........................................................................................................
Open File Dialog Box...............................................................................................................
Creating a New Language Definition with Oracle Locale Builder .............................................
Creating a New Territory Definition with the Oracle Locale Builder ........................................
Customizing Time Zone Data .....................................................................................................
Customizing Calendars with the NLS Calendar Utility..........................................................
Displaying a Code Chart with the Oracle Locale Builder...........................................................
Creating a New Character Set Definition with the Oracle Locale Builder ..............................
Character Sets with User-Defined Characters ..........................................................................
Oracle Database Character Set Conversion Architecture........................................................
Unicode 5.0 Private Use Area......................................................................................................
User-Defined Character Cross-References Between Character Sets......................................
Guidelines for Creating a New Character Set from an Existing Character Set....................
Example: Creating a New Character Set Definition with the Oracle Locale Builder..........
Creating a New Linguistic Sort with the Oracle Locale Builder................................................
Changing the Sort Order for All Characters with the Same Diacritic ...................................
Changing the Sort Order for One Character with a Diacritic .................................................
Generating and Installing NLB Files ..............................................................................................
Deploying Custom NLB Files on Other Platforms .......................................................................
Upgrading Custom NLB Files from Previous Releases of Oracle Database ...........................
Transporting NLB Data from One Platform to Another..............................................................
Adding Custom Locale Definitions to Java Components with the GINSTALL Utility .......

13-1
13-2
13-2
13-2
13-3
13-3
13-4
13-4
13-4
13-5
13-6
13-9
13-15
13-15
13-16
13-20
13-20
13-21
13-21
13-22
13-22
13-23
13-26
13-29
13-31
13-33
13-34
13-35
13-35
13-35

Locale Data
Languages .................................................................................................................................................
Translated Messages ...............................................................................................................................
Territories ..................................................................................................................................................
Character Sets...........................................................................................................................................
Recommended Database Character Sets .......................................................................................
Other Character Sets .........................................................................................................................
Character Sets that Support the Euro Symbol ............................................................................
Client-Only Character Sets ............................................................................................................
Universal Character Sets ................................................................................................................

A-1
A-3
A-4
A-5
A-6
A-8
A-12
A-14
A-15

xiii

Character Set Conversion Support ...............................................................................................
Subsets and Supersets.....................................................................................................................
Language and Character Set Detection Support .............................................................................
Linguistic Sorts ......................................................................................................................................
Calendar Systems ..................................................................................................................................
Time Zone Names..................................................................................................................................
Obsolete Locale Data ............................................................................................................................
Obsolete Linguistic Sorts................................................................................................................
Obsolete Territories.........................................................................................................................
Obsolete Languages ........................................................................................................................
Obsolete Character Sets and Replacement Character Sets........................................................
AL24UTFFSS Character Set Desupported ...................................................................................
Updates to the Oracle Database Language and Territory Definition Files.............................

A-16
A-16
A-18
A-19
A-22
A-23
A-29
A-29
A-29
A-29
A-29
A-31
A-31

Unicode Character Code Assignments
Unicode Code Ranges............................................................................................................................. B-1
UTF-16 Encoding ..................................................................................................................................... B-2
UTF-8 Encoding ....................................................................................................................................... B-2

Index

xiv

Preface
This book describes Oracle globalization support for Oracle Database. It explains how
to set up a globalization support environment, choose and migrate a character set,
customize locale data, do linguistic sorting, program in a global environment, and
program with Unicode.
This preface contains these topics:
■

Intended Audience

■

Documentation Accessibility

■

See Also:

■
■

Improved performance for character set conversion.
New report section for Database Character Set Scanner that provides information
about compact binary XML (CSX) data in the Data Dictionary.
See Also:

■

Chapter 12, "Character Set Scanner Utilities"

GINSTALL utility for adding customized locale files to Java components.

xxi

See Also:
■

Three new languages added: Albanian, Belarusian, and Irish, and two new
territories added: Albania and Belarus.
See Also:

■

Chapter 13, "Customizing Locale Data"

Appendix A, "Locale Data"

Linguistic index support for collation-sensitive SQL LIKE condition.
See Also:

Chapter 5, "Linguistic Sorting and String Searching"

Oracle Database 10g Release 2 (10.2) New Features in Globalization
■

Support for Unicode 4.0.
Unicode support has been enhanced to support the latest version of the Unicode
standard.
See Also: Chapter 6, "Supporting Multilingual Databases with
Unicode"

■

Character Set Scanner Utilities Enhancements
The Database Character Set Scanner (CSSCAN) introduces two new parameters,
QUERY and COLUMN, which offer finer control in performing selective scanning.
Support for multilevel varrays and nested tables has also been added.
The Language and Character Set File Scanner (LCSSCAN) now supports the
detection of HTML files. The detection quality of shorter text strings has also been
enhanced.
See Also:

■

Chapter 12, "Character Set Scanner Utilities"

Globalization Development Kit
The Globalization Development Kit (GDK) for PL/SQL provides new locale
mapping functions, and offers support for Japanese Kana conversion using the
new transliteration function in the UTL_I18N package.
See Also:

■

Chapter 8, "Oracle Globalization Development Kit"

NCHAR String Literal Support
SQL NCHAR literals used in insert and update statements no longer rely on the
database character set for conversion. This means that multilingual data can be
added without restrictions such as having to provide hex Unicode values. The
support for this feature is available in SQL, PL/SQL, OCI, and JDBC.
See Also: "NCHAR String Literal Replacement" in Chapter 7,
"Programming with Unicode"

■

Consistent Linguistic Ordering Support
The support for all SQL functions and operators to honor the NLS_SORT setting is
now available using the new NLS_COMP mode LINGUISTIC. This feature ensures
all SQL string comparisons are consistent, and that they follow the linguistic
convention as specified in the NLS_SORT parameter.

xxii

See Also:

Chapter 5, "Linguistic Sorting and String Searching"

xxiii

xxiv

1
Overview of Globalization Support
This chapter provides an overview of globalization support for Oracle Database. This
chapter discusses the following topics:
■

Globalization Support Architecture

■

Globalization Support Features

Globalization Support Architecture
The globalization support in Oracle Database enables you to store, process, and
retrieve data in native languages. It ensures that database utilities, error messages, sort
order, and date, time, monetary, numeric, and calendar conventions automatically
adapt to any native language and locale.
In the past, Oracle referred to globalization support capabilities as National Language
Support (NLS) features. NLS is actually a subset of globalization support. NLS is the
ability to choose a national language and store data in a specific character set.
Globalization support enables you to develop multilingual applications and software
products that can be accessed and run from anywhere in the world simultaneously. An
application can render content of the user interface and process data in the native
users' languages and locale preferences.

Locale Data on Demand
Oracle Database globalization support is implemented with the Oracle NLS Runtime
Library (NLSRTL). The NLS RTL provides a comprehensive suite of
language-independent functions that perform proper text and character processing
and language-convention manipulations. Behavior of these functions for a specific
language and territory is governed by a set of locale-specific data that is identified and
loaded at runtime.
The locale-specific data is structured as independent sets of data for each locale that
Oracle Database supports. The data for a particular locale can be loaded
independently of other locale data.
The advantages of this design are as follows:
■

■

You can manage memory consumption by choosing the set of locales that you
need.
You can add and customize locale data for a specific locale without affecting other
locales.

Overview of Globalization Support

1-1

Globalization Support Architecture

Figure 1–1 shows how locale-specific data is loaded at runtime. In this example,
French data and Japanese data are loaded into the multilingual database, but German
data is not.
Figure 1–1 Loading Locale-Specific Data to the Database

German
Data

ch
en ta
Fr Da

p
Da ane
ta s e

Multilingual
Database

French
Data

Japanese
Data

The locale-specific data is stored in the $ORACLE_HOME/nls/data directory. The
ORA_NLS10 environment variable should be defined only when you need to change
the default directory location for the locale-specific datafiles, for example, when the
system has multiple Oracle Database homes that share a single copy of the
locale-specific datafiles.
A boot file is used to determine the availability of the NLS objects that can be loaded.
Oracle Database supports both system and user boot files. The user boot file gives you
the flexibility to tailor what NLS locale objects are available for the database. Also, new
locale data can be added and some locale data components can be customized.
See Also:

Chapter 13, "Customizing Locale Data"

Architecture to Support Multilingual Applications
Oracle Database enables multitier applications and client/server applications to
support languages for which the database is configured.
The locale-dependent operations are controlled by several parameters and
environment variables on both the client and the database server. On the database
server, each session that is started on behalf of a client may run in the same or a
different locale as other sessions, and can have the same or different language
requirements specified.
Oracle Database has a set of session-independent NLS parameters that are specified
when you create a database. Two of the parameters specify the database character set
and the national character set, which is an alternative Unicode character set that can be
specified for NCHAR, NVARCHAR2, and NCLOB data. The parameters specify the
character set that is used to store text data in the database. Other parameters, such as
language and territory, are used to evaluate and check constraints.
If the client session and the database server specify different character sets, then the
database converts character set strings automatically.

1-2 Oracle Database Globalization Support Guide

Globalization Support Architecture

From a globalization support perspective, all applications are considered to be clients,
even if they run on the same physical machine as the Oracle Database instance. For
example, when SQL*Plus is started by the UNIX user who owns the Oracle Database
software from the Oracle home in which the RDBMS software is installed, and
SQL*Plus connects to the database through an adapter by specifying the ORACLE_SID
parameter, SQL*Plus is considered a client. Its behavior is ruled by client-side NLS
parameters.
Another example of an application being considered a client occurs when the middle
tier is an application server. The different sessions spawned by the application server
are considered to be separate client sessions.
When a client application is started, it initializes the client NLS environment from
environment settings. All NLS operations performed locally are executed using these
settings. Examples of local NLS operations are:
■

Display formatting in Oracle Developer applications

■

User OCI code that executes NLS OCI functions with OCI environment handles

When the application connects to a database, a session is created on the server. The
new session initializes its NLS environment from NLS instance parameters specified in
the initialization parameter file. These settings can be subsequently changed by an
ALTER SESSION statement. The statement changes only the session NLS environment.
It does not change the local client NLS environment. The session NLS settings are used
to process SQL and PL/SQL statements that are executed on the server. For example,
use an ALTER SESSION statement to set the NLS_LANGUAGE initialization parameter
to Italian:
ALTER SESSION SET NLS_LANGUAGE=Italian;

Enter a SELECT statement:
SQL> SELECT last_name, hire_date, ROUND(salary/8,2) salary FROM employees;

You should see results similar to the following:
LAST_NAME
------------------------Sciarra
Urman
Popp

HIRE_DATE
SALARY
--------- ---------30-SET-97
962.5
07-MAR-98
975
07-DIC-99
862.5

Note that the month name abbreviations are in Italian.
Immediately after the connection has been established, if the NLS_LANG environment
setting is defined on the client side, then an implicit ALTER SESSION statement
synchronizes the client and session NLS environments.
See Also:
■

Chapter 10, "OCI Programming in a Global Environment"

■

Chapter 3, "Setting Up a Globalization Support Environment"

Using Unicode in a Multilingual Database
Unicode, the universal encoded character set, enables you to store information in any
language by using a single character set. Unicode provides a unique code value for
every character, regardless of the platform, program, or language.
Unicode has the following advantages:

Overview of Globalization Support

1-3

Globalization Support Features

■

Simplifies character set conversion and linguistic sort functions.

■

Improves performance compared with native multibyte character sets.

■

Supports the Unicode datatype based on the Unicode standard.
See Also:
■

Chapter 6, "Supporting Multilingual Databases with Unicode"

■

Chapter 7, "Programming with Unicode"

■

"Enabling Multilingual Support with Unicode Datatypes" on
page 6-7

Globalization Support Features
This section provides an overview of the standard globalization features in Oracle
Database:
■

Language Support

■

Territory Support

■

Date and Time Formats

■

Monetary and Numeric Formats

■

Calendar Systems

■

Linguistic Sorting

■

Character Set Support

■

Character Semantics

■

Customization of Locale and Calendar Data

■

Unicode Support

Language Support
Oracle Database enables you to store, process, and retrieve data in native languages.
The languages that can be stored in a database are all languages written in scripts that
are encoded by Oracle-supported character sets. Through the use of Unicode
databases and datatypes, Oracle Database supports most contemporary languages.
Additional support is available for a subset of the languages. The database can, for
example, display dates using translated month names, and can sort text data according
to cultural conventions.
When this document uses the term language support, it refers to the additional
language-dependent functionality, and not to the ability to store text of a specific
language. For example, language support includes displaying dates or sorting text
according to specific locales and cultural conventions. Additionally, for some of the
supported languages, Oracle Database provides translated error messages and a
translated user interface for the database utilities.

1-4 Oracle Database Globalization Support Guide

Globalization Support Features

See Also:
■

■

"SQL Functions for Different Length Semantics" on page 9-5 for
more information about the SUBSTR and SUBSTRB functions
"Length Semantics" on page 3-31 for more information about
the NLS_LENGTH_SEMANTICS initialization parameter
Chapter 6, "Supporting Multilingual Databases with Unicode"
for more information about Unicode and the NCHAR datatype
Oracle Database SQL Reference for more information about the
SUBSTRB and SUBSTR functions and the BYTE and CHAR
qualifiers for character datatypes

Choosing an Oracle Database Character Set
Oracle Database uses the database character set for:
■

Data stored in SQL CHAR datatypes (CHAR, VARCHAR2, CLOB, and LONG)

■

Identifiers such as table names, column names, and PL/SQL variables

■

Entering and storing SQL and PL/SQL source code

The character encoding scheme used by the database is defined as part of the CREATE
DATABASE statement. All SQL CHAR datatype columns (CHAR, CLOB, VARCHAR2, and
LONG), including columns in the data dictionary, have their data stored in the
database character set. In addition, the choice of database character set determines
which characters can name objects in the database. SQL NCHAR datatype columns
(NCHAR, NCLOB, and NVARCHAR2) use the national character set.
After the database is created, you cannot change the character sets, with some
exceptions, without re-creating the database.
Consider the following questions when you choose an Oracle Database character set
for the database:
■

What languages does the database need to support now?

■

What languages does the database need to support in the future?

2-10 Oracle Database Globalization Support Guide

Choosing an Oracle Database Character Set

■

Is the character set available on the operating system?

■

What character sets are used on clients?

■

How well does the application handle the character set?

■

What are the performance implications of the character set?

■

What are the restrictions associated with the character set?

The Oracle Database character sets are listed in "Character Sets" on page A-5. They are
named according to the languages and regions in which they are used. Some character
sets that are named for a region are also listed explicitly by language.
If you want to see the characters that are included in a character set, then:
■

■

Check national, international, or vendor product documentation or standards
documents
Use Oracle Locale Builder

This section contains the following topics:
■

Current and Future Language Requirements

■

Client Operating System and Application Compatibility

■

Character Set Conversion Between Clients and the Server

■

Performance Implications of Choosing a Database Character Set

■

Restrictions on Database Character Sets

■

Choosing a National Character Set

■

Summary of Supported Datatypes
See Also:
■

"UCS-2 Encoding" on page 6-3

■

"Choosing a National Character Set" on page 2-14

■

"Changing the Character Set After Database Creation" on
page 2-15

■

Appendix A, "Locale Data"

■

Chapter 13, "Customizing Locale Data"

Current and Future Language Requirements
Several character sets may meet your current language requirements. Consider future
language requirements when you choose a database character set. If you expect to
support additional languages in the future, then choose a character set that supports
those languages to prevent the need to migrate to a different character set later.

Client Operating System and Application Compatibility
The database character set is independent of the operating system because Oracle
Database has its own globalization architecture. For example, on an English Windows
operating system, you can create and run a database with a Japanese character set.
However, when an application in the client operating system accesses the database, the
client operating system must be able to support the database character set with
appropriate fonts and input methods. For example, you cannot insert or retrieve
Japanese data on the English Windows operating system without first installing a

Choosing a Character Set 2-11

Choosing an Oracle Database Character Set

Japanese font and input method. Another way to insert and retrieve Japanese data is to
use a Japanese operating system remotely to access the database server.

Character Set Conversion Between Clients and the Server
If you choose a database character set that is different from the character set on the
client operating system, then the Oracle Database can convert the operating system
character set to the database character set. Character set conversion has the following
disadvantages:
■

Potential data loss

■

Increased overhead

Character set conversions can sometimes cause data loss. For example, if you are
converting from character set A to character set B, then the destination character set B
must have the same character set repertoire as A. Any characters that are not available
in character set B are converted to a replacement character. The replacement character
is often specified as a question mark or as a linguistically related character. For
example, ä (a with an umlaut) may be converted to a. If you have distributed
environments, then consider using character sets with similar character repertoires to
avoid loss of data.
Character set conversion may require copying strings between buffers several times
before the data reaches the client. The database character set should always be a
superset or equivalent of the native character set of the client's operating system. The
character sets used by client applications that access the database usually determine
which superset is the best choice.
If all client applications use the same character set, then that character set is usually the
best choice for the database character set. When client applications use different
character sets, the database character set should be a superset of all the client character
sets. This ensures that every character is represented when converting from a client
character set to the database character set.
See Also:

Chapter 11, "Character Set Migration"

Performance Implications of Choosing a Database Character Set
For best performance, choose a character set that avoids character set conversion and
uses the most efficient encoding for the languages desired. Single-byte character sets
result in better performance than multibyte character sets, and they also are the most
efficient in terms of space requirements. However, single-byte character sets limit how
many languages you can support.

Restrictions on Database Character Sets
ASCII-based character sets are supported only on ASCII-based platforms. Similarly,
you can use an EBCDIC-based character set only on EBCDIC-based platforms.
The database character set is used to identify SQL and PL/SQL source code. In order
to do this, it must have either EBCDIC or 7-bit ASCII as a subset, whichever is native
to the platform. Therefore, it is not possible to use a fixed-width, multibyte character
set as the database character set. Currently, only the AL16UTF16 character set cannot
be used as a database character set.

Restrictions on Character Sets Used to Express Names
Table 2–5 lists the restrictions on the character sets that can be used to express names.

2-12 Oracle Database Globalization Support Guide

Choosing an Oracle Database Character Set

Table 2–5

Restrictions on Character Sets Used to Express Names

Name

Single-Byte

Variable
Width

Comments

Column names

Yes

Schema objects

Yes

Comments

Yes

Database link names

Yes

Database names

Yes

File names (datafile, log file, control Yes
file, initialization parameter file)

Instance names

Yes

Directory names

Yes

Keywords

Yes

Can be expressed in English ASCII or EBCDIC
characters only

Recovery Manager file names

Yes

Rollback segment names

Yes

The ROLLBACK_SEGMENTS parameter does not
support NLS

Stored script names

Yes

Tablespace names

Yes

For a list of supported string formats and character sets, including LOB data (LOB,
BLOB, CLOB, and NCLOB), see Table 2–7 on page 2-14.

Database Character Set Statement of Direction
A list of character sets has been compiled in Table A–4, " Recommended ASCII
Database Character Sets" and Table A–5, " Recommended EBCDIC Database Character
Sets" that Oracle strongly recommends for usage as the database character set. Other
Oracle-supported character sets that do not appear on this list can continue to be used
in Oracle Database 11g Release 1, but may be desupported in a future release. Starting
with the next major functional release after Oracle Database 10g Release 2, the choice
for the database character set will be limited to this list of recommended character sets
for new system deployment. Customers will still be able to migrate their existing
databases in the next major functional release after Oracle Database 10g Release 2 even
if the character set is not on the recommended list. However, Oracle suggests that
customers migrate to a recommended character set as soon as possible. At the top of
the list of character sets that Oracle recommends for all new system deployment, is the
Unicode character set AL32UTF8.

Choosing Unicode as a Database Character Set
Oracle recommends using Unicode for all new system deployments. Migrating legacy
systems to Unicode is also recommended. Deploying your systems today in Unicode
offers many advantages in usability, compatibility, and extensibility. Oracle Database
enables you to deploy high-performing systems faster and more easily while utilizing
the advantages of Unicode. Even if you do not need to support multilingual data
today, nor have any requirement for Unicode, it is still likely to be the best choice for a
new system in the long run and will ultimately save you time and money as well as

Choosing a Character Set 2-13

Choosing an Oracle Database Character Set

give you competitive advantages in the long term. See Chapter 6, "Supporting
Multilingual Databases with Unicode" for more information about Unicode.

Choosing a National Character Set
The term national character set refers to an alternative character set that enables you
to store Unicode character data in a database that does not have a Unicode database
character set. Other reasons for choosing a national character set are:
■

■

The properties of a different character encoding scheme may be more desirable for
extensive character processing operations.
Programming in the national character set is easier.

SQL NCHAR, NVARCHAR2, and NCLOB datatypes support Unicode data only. You can
use either the UTF8 or the AL16UTF16 character set. The default is AL16UTF16.
See Also: Chapter 6, "Supporting Multilingual Databases with
Unicode"

Summary of Supported Datatypes
Table 2–6 lists the datatypes that are supported for different encoding schemes.
Table 2–6

SQL Datatypes Supported for Encoding Schemes

Datatype

Single Byte

Multibyte Non-Unicode

Multibyte Unicode

CHAR

Yes

VARCHAR2

Yes

NCHAR

Yes

NVARCHAR2

Yes

BLOB

Yes

CLOB

Yes

LONG

Yes

NCLOB

Yes

BLOBs process characters as a series of byte sequences.
The data is not subject to any NLS-sensitive operations.

Note:

Table 2–7 lists the SQL datatypes that are supported for abstract datatypes.
Table 2–7

Abstract Datatype Support for SQL Datatypes

Abstract Datatype

CHAR

NCHAR

BLOB

CLOB

NCLOB

Object

Yes

Collection

Yes

You can create an abstract datatype with the NCHAR attribute as follows:
SQL> CREATE TYPE tp1 AS OBJECT (a NCHAR(10));
Type created.
SQL> CREATE TABLE t1 (a tp1);
Table created.

2-14 Oracle Database Globalization Support Guide

Monolingual Database Scenario

See Also: Oracle Database Application Developer's Guide Object-Relational Features for more information about objects and
collections

Changing the Character Set After Database Creation
You may wish to change the database character set after the database has been created.
For example, you may find that the number of languages that need to be supported in
your database has increased. In most cases, you need to do a full export/import to
properly convert all data to the new character set. However, if, and only if, the new
character set is a strict superset of all of the schema data, then it is possible to use the
CSALTER script to expedite the change in the database character set.
See Also:
■
■

■

Chapter 11, "Character Set Migration"
Oracle Database Upgrade Guide for more information about
exporting and importing data
Oracle Streams Concepts and Administration for information
about using Streams to change the character set of a database
while the database remains online

Monolingual Database Scenario
The simplest example of a database configuration is a client and a server that run in
the same language environment and use the same character set. This monolingual
scenario has the advantage of fast response because the overhead associated with
character set conversion is avoided. Figure 2–3 shows a database server and a client
that use the same character set. The Japanese client and the server both use the
JA16EUC character set.
Figure 2–3 Monolingual Database Scenario

Japanese
Server
(JA16EUC)

Unix
(JA16EUC)

You can also use a multitier architecture. Figure 2–4 shows an application server
between the database server and the client. The application server and the database
server use the same character set in a monolingual scenario. The server, the application
server, and the client use the JA16EUC character set.

Choosing a Character Set 2-15

Monolingual Database Scenario

Figure 2–4 Multitier Monolingual Database Scenario

Japanese
Server
(JA16EUC)

Browser

Application
Server
(JA16EUC)

Character Set Conversion in a Monolingual Scenario
Character set conversion may be required in a client/server environment if a client
application resides on a different platform than the server and if the platforms do not
use the same character encoding schemes. Character data passed between client and
server must be converted between the two encoding schemes. Character conversion
occurs automatically and transparently through Oracle Net.
You can convert between any two character sets. Figure 2–5 shows a server and one
client with the JA16EUC Japanese character set. The other client uses the JA16SJIS
Japanese character set.
Figure 2–5 Character Set Conversion

Japanese
Server
(JA16EUC)
Unix
(JA16EUC)
Character
Conversion

Windows
(JA16SJIS)

When a target character set does not contain all of the characters in the source data,
replacement characters are used. If, for example, a server uses US7ASCII and a
German client uses WE8ISO8859P1, then the German character ß is replaced with ?
and ä is replaced with a.
Replacement characters may be defined for specific characters as part of a character set
definition. When a specific replacement character is not defined, a default replacement
character is used. To avoid the use of replacement characters when converting from a
client character set to a database character set, the server character set should be a
superset of all the client character sets.
Figure 2–6 shows that data loss occurs when the database character set does not
include all of the characters in the client character set. The database character set is
US7ASCII. The client's character set is WE8MSWIN1252, and the language used by the
client is German. When the client inserts a string that contains ß, the database replaces
ß with ?, resulting in lost data.

2-16 Oracle Database Globalization Support Guide

Multilingual Database Scenarios

Figure 2–6 Data Loss During Character Conversion

American
Database
Server
(US7ASCII)

?
Character
Conversion

German
Windows
(WE8MSWIN1252)

If German data is expected to be stored on the server, then a database character set that
supports German characters should be used for both the server and the client to avoid
data loss and conversion overhead.
When one of the character sets is a variable-width multibyte character set, conversion
can introduce noticeable overhead. Carefully evaluate your situation and choose
character sets to avoid conversion as much as possible.

Multilingual Database Scenarios
Multilingual support can be restricted or unrestricted. This section contains the
following topics:
■

Restricted Multilingual Support

■

Unrestricted Multilingual Support

Restricted Multilingual Support
Some character sets support multiple languages because they have related writing
systems or scripts. For example, the Oracle Database WE8ISO8859P1 character set
supports the following Western European languages:
Catalan
Danish
Dutch
English
Finnish
French
German
Icelandic
Italian
Norwegian
Portuguese
Spanish

Choosing a Character Set 2-17

Multilingual Database Scenarios

Swedish
These languages all use a Latin-based writing script.
When you use a character set that supports a group of languages, your database has
restricted multilingual support.
Figure 2–7 shows a Western European server that used the WE8ISO8850P1 Oracle
Database character set, a French client that uses the same character set as the server,
and a German client that uses the WE8DEC character set. The German client requires
character conversion because it is using a different character set than the server.
Figure 2–7 Restricted Multilingual Support
(WE8ISO8859P1)

Western
European
Server

Character
Conversion

French
(WE8ISO8859P1)

German
(WE8DEC)

Unrestricted Multilingual Support
If you need unrestricted multilingual support, then use a universal character set such
as Unicode for the server database character set. Unicode has two major encoding
schemes:
■

UTF-16: Each character is either 2 or 4 bytes long.

■

UTF-8: Each character takes 1 to 4 bytes to store.

Oracle Database provides support for UTF-8 as a database character set and both
UTF-8 and UTF-16 as national character sets.
Character set conversion between a UTF-8 database and any single-byte character set
introduces very little overhead.
Conversion between UTF-8 and any multibyte character set has some overhead. There
is no data loss from conversion, with the following exceptions:
■

■

Some multibyte character sets do not support user-defined characters during
character set conversion to and from UTF-8.
Some Unicode characters are mapped to more than one character in another
character set. For example, one Unicode character is mapped to three characters in
the JA16SJIS character set. This means that a round-trip conversion may not result
in the original JA16SJIS character.

2-18 Oracle Database Globalization Support Guide

Multilingual Database Scenarios

Figure 2–8 shows a server that uses the AL32UTF8 Oracle Database character set that
is based on the Unicode UTF-8 character set.
Figure 2–8 Unrestricted Multilingual Support Scenario in a Client/Server Configuration

German
Client
(WE8DEC)

French
Client
(WE8ISO8859P1)
Character
Conversion

Character
Conversion

Unicode
Database
(AL32UTF8)

Character
Conversion

Japanese
Client
(JA16EUC)

Character
Conversion

Japanese
Client
(JA16SJIS)

There are four clients:
■

A French client that uses the WE8ISO8859P1 Oracle Database character set

■

A German client that uses the WE8DEC character set

■

A Japanese client that uses the JA16EUC character set

■

A Japanese client that used the JA16SJIS character set

Character conversion takes place between each client and the server, but there is no
data loss because AL32UTF8 is a universal character set. If the German client tries to
retrieve data from one of the Japanese clients, then all of the Japanese characters in the
data are lost during the character set conversion.
Figure 2–9 shows a Unicode solution for a multitier configuration.

Choosing a Character Set 2-19

Multilingual Database Scenarios

Figure 2–9 Multitier Unrestricted Multilingual Support Scenario in a Multitier
Configuration
French
Client
Browser
(UTF-8)

German
Client
(UTF-8)

Unicode
Database
(AL32UTF8)

Browser

Application
Server
(UTF-8)
(UTF-8)

Japanese
Client
Browser

The database, the application server, and each client use the AL32UTF8 character set.
This eliminates the need for character conversion even though the clients are French,
German, and Japanese.
See Also: Chapter 6, "Supporting Multilingual Databases with
Unicode"

2-20 Oracle Database Globalization Support Guide

3
Setting Up a Globalization Support
Environment
This chapter tells how to set up a globalization support environment. It includes the
following topics:
■

Setting NLS Parameters

■

Choosing a Locale with the NLS_LANG Environment Variable

■

NLS Database Parameters

■

Language and Territory Parameters

■

Date and Time Parameters

■

Calendar Definitions

■

Numeric and List Parameters

■

Monetary Parameters

■

Linguistic Sort Parameters

■

Character Set Conversion Parameter

■

Length Semantics

Setting NLS Parameters
NLS (National Language Support) parameters determine the locale-specific behavior
on both the client and the server. NLS parameters can be specified in the following
ways:
■

As initialization parameters on the server
You can include parameters in the initialization parameter file to specify a default
session NLS environment. These settings have no effect on the client side; they
control only the server's behavior. For example:
NLS_TERRITORY = "CZECH REPUBLIC"

■

As environment variables on the client
You can use NLS environment variables, which may be platform-dependent, to
specify locale-dependent behavior for the client and also to override the default
values set for the session in the initialization parameter file. For example, on a
UNIX system:
% setenv NLS_SORT FRENCH

Setting Up a Globalization Support Environment

3-1

Setting NLS Parameters

■

With the ALTER SESSION statement
You can use NLS parameters that are set in an ALTER SESSION statement to
override the default values that are set for the session in the initialization
parameter file or set by the client with environment variables.
ALTER SESSION SET NLS_SORT = FRENCH;

Oracle Database SQL Reference for more information
about the ALTER SESSION statement

See Also:

■

In SQL functions
You can use NLS parameters explicitly to hardcode NLS behavior within a SQL
function. This practice overrides the default values that are set for the session in
the initialization parameter file, set for the client with environment variables, or
set for the session by the ALTER SESSION statement. For example:
TO_CHAR(hiredate, 'DD/MON/YYYY', 'nls_date_language = FRENCH')

Oracle Database SQL Reference for more information
about SQL functions, including the TO_CHAR function

See Also:

Table 3–1 shows the precedence order of the different methods of setting NLS
parameters. Higher priority settings override lower priority settings. For example, a
default value has the lowest priority and can be overridden by any other method.
Table 3–1

Methods of Setting NLS Parameters and Their Priorities

Priority

Method

1 (highest)

Explicitly set in SQL functions

Set by an ALTER SESSION statement

Set as an environment variable

Specified in the initialization parameter file

Default

Table 3–2 lists the available NLS parameters. Because the SQL function NLS
parameters can be specified only with specific functions, the table does not show the
SQL function scope.
Table 3–2

NLS Parameters
Scope:

Parameter

Description

Default

I = Initialization Parameter File
E = Environment Variable
A = ALTER SESSION

NLS_CALENDAR

Calendar system

Gregorian

I, E, A

NLS_COMP

SQL, PL/SQL operator
comparison

BINARY

I, E, A

NLS_CREDIT

Credit accounting symbol

Derived from
NLS_TERRITORY

NLS_CURRENCY

Local currency symbol

Derived from
I, E, A
NLS_TERRITORY

NLS_DATE_FORMAT

Date format

Derived from
I, E, A
NLS_TERRITORY

3-2 Oracle Database Globalization Support Guide

Choosing a Locale with the NLS_LANG Environment Variable

Table 3–2 (Cont.) NLS Parameters
Scope:
I = Initialization Parameter File
E = Environment Variable
A = ALTER SESSION

Parameter

Description

Default

NLS_DATE_LANGUAGE

Language for day and month
names

Derived from
NLS_LANGUAGE

NLS_DEBIT

Debit accounting symbol

Derived from
E
NLS_TERRITORY

NLS_ISO_CURRENCY

ISO international currency
symbol

Derived from
I, E, A
NLS_TERRITORY

NLS_LANG

Language, territory, character AMERICAN_
set
AMERICA.
US7ASCII

NLS_LANGUAGE

Language

Derived from
NLS_LANG

I, A

NLS_LENGTH_
SEMANTICS

How strings are treated

BYTE

I, E, A

NLS_LIST_SEPARATOR

Character that separates items Derived from
E
in a list
NLS_TERRITORY

NLS_MONETARY_
CHARACTERS

Monetary symbol for dollar
and cents (or their
equivalents)

Derived from
E
NLS_TERRITORY

NLS_NCHAR_CONV_
EXCP

Reports data loss during a
character type conversion

FALSE

NLS_NUMERIC_
CHARACTERS

Decimal character and group
separator

Derived from
I, E, A
NLS_TERRITORY

NLS_SORT

Character sort sequence

Derived from
NLS_LANGUAGE

I, E, A

NLS_TERRITORY

Territory

Derived from
NLS_LANG

I, A

NLS_TIMESTAMP_
FORMAT

Timestamp

Derived from
I, E, A
NLS_TERRITORY

NLS_TIMESTAMP_TZ_
FORMAT

Timestamp with time zone

Derived from
I, E, A
NLS_TERRITORY

NLS_DUAL_CURRENCY

Dual currency symbol

Derived from
I, E, A
NLS_TERRITORY

See Also: "Choosing a
Locale with the NLS_LANG
Environment Variable" on
page 3-3

I, E, A

I, A

Choosing a Locale with the NLS_LANG Environment Variable
A locale is a linguistic and cultural environment in which a system or program is
running. Setting the NLS_LANG environment parameter is the simplest way to specify
locale behavior for Oracle Database software. It sets the language and territory used by
the client application and the database server. It also sets the client's character set,
which is the character set for data entered or displayed by a client program.
NLS_LANG is set as an environment variable on UNIX platforms. NLS_LANG is set in
the registry on Windows platforms.

Setting Up a Globalization Support Environment

3-3

Choosing a Locale with the NLS_LANG Environment Variable

The NLS_LANG parameter has three components: language, territory, and character set.
Specify it in the following format, including the punctuation:
NLS_LANG = language_territory.charset

For example, if the Oracle Universal Installer does not populate NLS_LANG, then its
value by default is AMERICAN_AMERICA.US7ASCII. The language is AMERICAN, the
territory is AMERICA, and the character set is US7ASCII. The values in NLS_LANG and
other NLS parameters are case-insensitive.
Each component of the NLS_LANG parameter controls the operation of a subset of
globalization support features:
■

language
Specifies conventions such as the language used for Oracle Database messages,
sorting, day names, and month names. Each supported language has a unique
name; for example, AMERICAN, FRENCH, or GERMAN. The language argument
specifies default values for the territory and character set arguments. If the
language is not specified, then the value defaults to AMERICAN.

■

territory
Specifies conventions such as the default date, monetary, and numeric formats.
Each supported territory has a unique name; for example, AMERICA, FRANCE, or
CANADA. If the territory is not specified, then the value is derived from the
language value.

■

charset
Specifies the character set used by the client application (normally the Oracle
Database character set that corresponds to the user's terminal character set or the
OS character set). Each supported character set has a unique acronym, for
example, US7ASCII, WE8ISO8859P1, WE8DEC, WE8MSWIN1252, or JA16EUC.
Each language has a default character set associated with it.
All components of the NLS_LANG definition are optional;
any item that is not specified uses its default value. If you specify
territory or character set, then you must include the preceding
delimiter [underscore (_) for territory, period (.) for character set].
Otherwise, the value is parsed as a language name.

Note:

For example, to set only the territory portion of NLS_LANG, use the
following format: NLS_LANG=_JAPAN
The three components of NLS_LANG can be specified in many combinations, as in the
following examples:
NLS_LANG = AMERICAN_AMERICA.WE8MSWIN1252
NLS_LANG = FRENCH_CANADA.WE8ISO8859P1
NLS_LANG = JAPANESE_JAPAN.JA16EUC

Note that illogical combinations can be set but do not work properly. For example, the
following specification tries to support Japanese by using a Western European
character set:
NLS_LANG = JAPANESE_JAPAN.WE8ISO8859P1

3-4 Oracle Database Globalization Support Guide

Choosing a Locale with the NLS_LANG Environment Variable

Because the WE8ISO8859P1 character set does not support any Japanese characters,
you cannot store or display Japanese data if you use this definition for NLS_LANG.
The rest of this section includes the following topics:
■

Specifying the Value of NLS_LANG

■

Overriding Language and Territory Specifications

■

Locale Variants
See Also:
■

■

Appendix A, "Locale Data" for a complete list of supported
languages, territories, and character sets
Your operating system documentation for information about
additional globalization settings that may be necessary for your
platform

Specifying the Value of NLS_LANG
In a UNIX operating system C-shell session, you can specify the value of NLS_LANG by
entering a statement similar to the following example:
% setenv NLS_LANG FRENCH_FRANCE.WE8ISO8859P1

Because NLS_LANG is an environment variable, it is read by the client application at
startup time. The client communicates the information defined by NLS_LANG to the
server when it connects to the database server.
The following examples show how date and number formats are affected by the NLS_
LANG parameter.
Example 3–1 Setting NLS_LANG to American_America.WE8ISO8859P1

Set NLS_LANG so that the language is AMERICAN, the territory is AMERICA, and the
Oracle Database character set is WE8ISO8859P1:
% setenv NLS_LANG American_America.WE8ISO8859P1

Enter a SELECT statement:
SQL> SELECT last_name, hire_date, ROUND(salary/8,2) salary FROM employees;

You should see results similar to the following output:
LAST_NAME
------------------------Sciarra
Urman
Popp

HIRE_DATE
SALARY
--------- ---------30-SEP-97
962.5
07-MAR-98
975
07-DEC-99
862.5

Example 3–2 Setting NLS_LANG to French_France.WE8ISO8859P1

Set NLS_LANG so that the language is FRENCH, the territory is FRANCE, and the Oracle
Database character set is WE8ISO8859P1:
% setenv NLS_LANG French_France.WE8ISO8859P1

Then the query shown in Example 3–1 returns the following output:
LAST_NAME
HIRE_DAT
SALARY
------------------------- -------- ----------

Setting Up a Globalization Support Environment

3-5

Choosing a Locale with the NLS_LANG Environment Variable

Sciarra
Urman
Popp

30/09/97
07/03/98
07/12/99

962,5
975
862,5

Note that the date format and the number format have changed. The numbers have
not changed, because the underlying data is the same.

Overriding Language and Territory Specifications
The NLS_LANG parameter sets the language and territory environment used by both
the server session (for example, SQL command execution) and the client application
(for example, display formatting in Oracle Database tools). Using this parameter
ensures that the language environments of both the database and the client application
are automatically the same.
The language and territory components of the NLS_LANG parameter determine the
default values for other detailed NLS parameters, such as date format, numeric
characters, and linguistic sorting. Each of these detailed parameters can be set in the
client environment to override the default values if the NLS_LANG parameter has
already been set.
If the NLS_LANG parameter is not set, then the server session environment remains
initialized with values of NLS_LANGUAGE, NLS_TERRITORY, and other NLS instance
parameters from the initialization parameter file. You can modify these parameters
and restart the instance to change the defaults.
You might want to modify the NLS environment dynamically during the session. To
do so, you can use the ALTER SESSION statement to change NLS_LANGUAGE, NLS_
TERRITORY, and other NLS parameters.
You cannot modify the setting for the client character set
with the ALTER SESSION statement.

Note:

The ALTER SESSION statement modifies only the session environment. The local
client NLS environment is not modified, unless the client explicitly retrieves the new
settings and modifies its local environment.
See Also:
■

■

"Overriding Default Values for NLS_LANGUAGE and NLS_
TERRITORY During a Session" on page 3-13
Oracle Database SQL Reference

Locale Variants
Before Oracle Database 10g, Oracle defined language and territory definitions
separately. This resulted in the definition of a territory being independent of the
language setting of the user. In Oracle Database 10g, some territories can have different
date, time, number, and monetary formats based on the language setting of a user.
This type of language-dependent territory definition is called a locale variant.
For the variant to work properly, both NLS_TERRITORY and NLS_LANGUAGE must be
specified.
Table 3–3 shows the territories that have been enhanced to support variations.

3-6 Oracle Database Globalization Support Guide

Choosing a Locale with the NLS_LANG Environment Variable

Table 3–3

Oracle Database Locale Variants

Oracle Database Territory

Oracle Database Language

BELGIUM

DUTCH

BELGIUM

FRENCH

BELGIUM

GERMAN

CANADA

FRENCH

CANADA

ENGLISH

DJIBOUTI

FRENCH

DJIBOUTI

ARABIC

FINLAND

SWEDISH

HONG KONG

TRADITIONAL CHINESE

HONG KONG

ENGLISH

INDIA

ENGLISH

INDIA

ASSAMESE

INDIA

BANGLA

INDIA

GUJARATI

INDIA

HINDI

INDIA

KANNADA

INDIA

MALAYALAM

INDIA

MARATHI

INDIA

ORIYA

INDIA

PUNJABI

INDIA

TAMIL

INDIA

TELUGU

LUXEMBOURG

GERMAN

LUXEMBOURG

FRENCH

SINGAPORE

ENGLISH

SINGAPORE

MALAY

SINGAPORE

SIMPLIFIED CHINESE

SINGAPORE

TAMIL

SWITZERLAND

GERMAN

SWITZERLAND

FRENCH

SWITZERLAND

ITALIAN

Should the NLS_LANG Setting Match the Database Character Set?
The NLS_LANG character set should reflect the setting of the operating system
character set of the client. For example, if the database character set is AL32UTF8 and
the client is running on a Windows operating system, then you should not set
AL32UTF8 as the client character set in the NLS_LANG parameter because there are no

Setting Up a Globalization Support Environment

3-7

NLS Database Parameters

UTF-8 WIN32 clients. Instead, the NLS_LANG setting should reflect the code page of
the client. For example, on an English Windows client, the code page is 1252. An
appropriate setting for NLS_LANG is AMERICAN_AMERICA.WE8MSWIN1252.
Setting NLS_LANG correctly enables proper conversion from the client operating
system character set to the database character set. When these settings are the same,
Oracle Database assumes that the data being sent or received is encoded in the same
character set as the database character set, so character set validation or conversion
may not be performed. This can lead to corrupt data if the client code page and the
database character set are different and conversions are necessary.
See Also: Oracle Database Installation Guide for 32-Bit Windows for
more information about commonly used values of the NLS_LANG
parameter in Windows

NLS Database Parameters
When a new database is created during the execution of the CREATE DATABASE
statement, the NLS-related database configuration is established. The current NLS
instance parameters are stored in the data dictionary along with the database and
national character sets. The NLS instance parameters are read from the initialization
parameter file at instance startup.
You can find the values for NLS parameters by using:
■

NLS Data Dictionary Views

■

NLS Dynamic Performance Views

■

OCINlsGetInfo() Function

NLS Data Dictionary Views
Applications can check the session, instance, and database NLS parameters by
querying the following data dictionary views:
■

■

NLS_SESSION_PARAMETERS shows the NLS parameters and their values for the
session that is querying the view. It does not show information about the character
set.
NLS_INSTANCE_PARAMETERS shows the current NLS instance parameters that
have been explicitly set and the values of the NLS instance parameters.
NLS_DATABASE_PARAMETERS shows the values of the NLS parameters for the
database. The values are stored in the database.

NLS Dynamic Performance Views
Applications can check the following NLS dynamic performance views:
■

■

V$NLS_VALID_VALUES lists values for the following NLS parameters: NLS_
LANGUAGE, NLS_SORT, NLS_TERRITORY, NLS_CHARACTERSET
V$NLS_PARAMETERS shows current values of the following NLS parameters:
NLS_CALENDAR, NLS_CHARACTERSET, NLS_CURRENCY, NLS_DATE_FORMAT,
NLS_DATE_LANGUAGE, NLS_ISO_CURRENCY, NLS_LANGUAGE, NLS_NUMERIC_
CHARACTERS, NLS_SORT, NLS_TERRITORY, NLS_NCHAR_CHARACTERSET, NLS_
COMP, NLS_LENGTH_SEMANTICS, NLS_NCHAR_CONV_EXP, NLS_TIMESTAMP_
FORMAT, NLS_TIMESTAMP_TZ_FORMAT, NLS_TIME_FORMAT, NLS_TIME_TZ_
FORMAT

3-8 Oracle Database Globalization Support Guide

Language and Territory Parameters

See Also:

Oracle Database Reference

OCINlsGetInfo() Function
User applications can query client NLS settings with the OCINlsGetInfo() function.
"Getting Locale Information in OCI" on page 10-2 for
the description of OCINlsGetInfo()

See Also:

Language and Territory Parameters
This section contains information about the following parameters:
■

NLS_LANGUAGE

■

NLS_TERRITORY

NLS_LANGUAGE
Property

Description

Parameter type

String

Parameter scope

Initialization parameter and ALTER SESSION

Default value

Derived from NLS_LANG

Range of values

Any valid language name

NLS_LANGUAGE specifies the default conventions for the following session
characteristics:
■
■

■

Language for server messages
Language for day and month names and their abbreviations (specified in the SQL
functions TO_CHAR and TO_DATE)
Symbols for equivalents of AM, PM, AD, and BC. (A.M., P.M., A.D., and B.C. are
valid only if NLS_LANGUAGE is set to AMERICAN.)
Default sorting sequence for character data when ORDER BY is specified. (GROUP
BY uses a binary sort unless ORDER BY is specified.)

■

Writing direction

■

Affirmative and negative response strings (for example, YES and NO)

The value specified for NLS_LANGUAGE in the initialization parameter file is the
default for all sessions in that instance. For example, to specify the default session
language as French, the parameter should be set as follows:
NLS_LANGUAGE = FRENCH

Consider the following server message:
ORA-00942: table or view does not exist

When the language is French, the server message appears as follows:
ORA-00942: table ou vue inexistante

Messages used by the server are stored in binary-format files that are placed in the
$ORACLE_HOME/product_name/mesg directory, or the equivalent for your
Setting Up a Globalization Support Environment

3-9

Language and Territory Parameters

operating system. Multiple versions of these files can exist, one for each supported
language, using the following filename convention:
.MSB

For example, the file containing the server messages in French is called oraf.msb,
because ORA is the product ID () and F is the language abbreviation
() for French. The product_name is rdbms, so it is in the
$ORACLE_HOME/rdbms/mesg directory.
If NLS_LANG is specified in the client environment, then the value of NLS_LANGUAGE
in the initialization parameter file is overridden at connection time.
Messages are stored in these files in one specific character set, depending on the
language and the operating system. If this character set is different from the database
character set, then message text is automatically converted to the database character
set. If necessary, it is then converted to the client character set if the client character set
is different from the database character set. Hence, messages are displayed correctly at
the user's terminal, subject to the limitations of character set conversion.
The language-specific binary message files that are actually installed depend on the
languages that the user specifies during product installation. Only the English binary
message file and the language-specific binary message files specified by the user are
installed.
The default value of NLS_LANGUAGE may be specific to the operating system. You can
alter the NLS_LANGUAGE parameter by changing its value in the initialization
parameter file and then restarting the instance.
See Also: Your operating system-specific Oracle Database
documentation for more information about the default value of
NLS_LANGUAGE

All messages and text should be in the same language. For example, when you run an
Oracle Developer application, the messages and boilerplate text that you see originate
from three sources:
■

Messages from the server

■

Messages and boilerplate text generated by Oracle Forms

■

Messages and boilerplate text generated by the application

NLS_LANGUAGE determines the language used for the first two kinds of text. The
application is responsible for the language used in its messages and boilerplate text.
The following examples show behavior that results from setting NLS_LANGUAGE to
different values.
Example 3–3 NLS_LANGUAGE=ITALIAN

Use the ALTER SESSION statement to set NLS_LANGUAGE to Italian:
ALTER SESSION SET NLS_LANGUAGE=Italian;

Enter a SELECT statement:
SQL> SELECT last_name, hire_date, ROUND(salary/8,2) salary FROM employees;

You should see results similar to the following output:
LAST_NAME
HIRE_DATE
SALARY
------------------------- --------- ----------

3-10 Oracle Database Globalization Support Guide

Language and Territory Parameters

Sciarra
Urman
Popp

30-SET-97
07-MAR-98
07-DIC-99

962.5
975
862.5

Note that the month name abbreviations are in Italian.
See Also: "Overriding Default Values for NLS_LANGUAGE and
NLS_TERRITORY During a Session" on page 3-13 for more
information about using the ALTER SESSION statement
Example 3–4 NLS_LANGUAGE=GERMAN

Use the ALTER SESSION statement to change the language to German:
SQL> ALTER SESSION SET NLS_LANGUAGE=German;

Enter the same SELECT statement:
SQL> SELECT last_name, hire_date, ROUND(salary/8,2) salary FROM employees;

You should see results similar to the following output:
LAST_NAME
------------------------Sciarra
Urman
Popp

HIRE_DATE
SALARY
--------- ---------30-SEP-97
962.5
07-MÄR-98
975
07-DEZ-99
862.5

Note that the language of the month abbreviations has changed.

NLS_TERRITORY
Property

Description

Parameter type

String

Parameter scope

Initialization parameter and ALTER SESSION

Default value

Derived from NLS_LANG

Range of values

Any valid territory name

NLS_TERRITORY specifies the conventions for the following default date and numeric
formatting characteristics:
■

Date format

■

Decimal character and group separator

■

Local currency symbol

■

ISO currency symbol

■

Dual currency symbol

■

First day of the week

■

Credit and debit symbols

■

ISO week flag

■

List separator

Setting Up a Globalization Support Environment

3-11

Language and Territory Parameters

The value specified for NLS_TERRITORY in the initialization parameter file is the
default for the instance. For example, to specify the default as France, the parameter
should be set as follows:
NLS_TERRITORY = FRANCE

When the territory is FRANCE, numbers are formatted using a comma as the decimal
character.
You can alter the NLS_TERRITORY parameter by changing the value in the
initialization parameter file and then restarting the instance. The default value of NLS_
TERRITORY can be specific to the operating system.
If NLS_LANG is specified in the client environment, then the value of NLS_TERRITORY
in the initialization parameter file is overridden at connection time.
The territory can be modified dynamically during the session by specifying the new
NLS_TERRITORY value in an ALTER SESSION statement. Modifying NLS_
TERRITORY resets all derived NLS session parameters to default values for the new
territory.
To change the territory to France during a session, issue the following ALTER
SESSION statement:
ALTER SESSION SET NLS_TERRITORY = France;

The following examples show behavior that results from different settings of NLS_
TERRITORY and NLS_LANGUAGE.
Example 3–5 NLS_LANGUAGE=AMERICAN, NLS_TERRITORY=AMERICA

Enter the following SELECT statement:
SQL> SELECT TO_CHAR(salary,'L99G999D99') salary FROM employees;

When NLS_TERRITORY is set to AMERICA and NLS_LANGUAGE is set to AMERICAN,
results similar to the following should appear:
SALARY
-------------------$24,000.00
$17,000.00
$17,000.00
Example 3–6 NLS_LANGUAGE=AMERICAN, NLS_TERRITORY=GERMANY

Use an ALTER SESSION statement to change the territory to Germany:
ALTER SESSION SET NLS_TERRITORY = Germany;
Session altered.

Enter the same SELECT statement as before:
SQL> SELECT TO_CHAR(salary,'L99G999D99') salary FROM employees;

You should see results similar to the following output:
SALARY
-------------------€24.000,00
€17.000,00
€17.000,00

3-12 Oracle Database Globalization Support Guide

Language and Territory Parameters

Note that the currency symbol has changed from $ to €. The numbers have not
changed because the underlying data is the same.
See Also: "Overriding Default Values for NLS_LANGUAGE and
NLS_TERRITORY During a Session" on page 3-13 for more
information about using the ALTER SESSION statement
Example 3–7 NLS_LANGUAGE=GERMAN, NLS_TERRITORY=GERMANY

Use an ALTER SESSION statement to change the language to German:
ALTER SESSION SET NLS_LANGUAGE = German;
Sitzung wurde geändert.

Note that the server message now appears in German.
Enter the same SELECT statement as before:
SQL> SELECT TO_CHAR(salary,'L99G999D99') salary FROM employees;

You should see the same results as in Example 3–6:
SALARY
-------------------€24.000,00
€17.000,00
€17.000,00
Example 3–8 NLS_LANGUAGE=GERMAN, NLS_TERRITORY=AMERICA

Use an ALTER SESSION statement to change the territory to America:
ALTER SESSION SET NLS_TERRITORY = America;
Sitzung wurde geändert.

Enter the same SELECT statement as in the other examples:
SQL> SELECT TO_CHAR(salary,'L99G999D99') salary FROM employees;

You should see results similar to the following output:
SALARY
-------------------$24,000.00
$17,000.00
$17,000.00

Note that the currency symbol changed from € to $ because the territory changed from
Germany to America.

Overriding Default Values for NLS_LANGUAGE and NLS_TERRITORY During a
Session
Default values for NLS_LANGUAGE and NLS_TERRITORY and default values for
specific formatting parameters can be overridden during a session by using the ALTER
SESSION statement.
Example 3–9 NLS_LANG=ITALIAN_ITALY.WE8DEC

Set the NLS_LANG environment variable so that the language is Italian, the territory is
Italy, and the character set is WE8DEC:
% setenv NLS_LANG Italian_Italy.WE8DEC

Setting Up a Globalization Support Environment

3-13

Language and Territory Parameters

Enter a SELECT statement:
SQL> SELECT last_name, hire_date, ROUND(salary/8,2) salary FROM employees;

You should see results similar to the following output:
LAST_NAME
------------------------Sciarra
Urman
Popp

HIRE_DATE
SALARY
--------- ---------30-SET-97
962,5
07-MAR-98
975
07-DIC-99
862,5

Note the language of the month abbreviations and the decimal character.
Example 3–10

Change Language, Date Format, and Decimal Character

Use ALTER SESSION statements to change the language, the date format, and the
decimal character:
SQL> ALTER SESSION SET NLS_LANGUAGE=german;
Session wurde geändert.
SQL> ALTER SESSION SET NLS_DATE_FORMAT='DD.MON.YY';
Session wurde geändert.
SQL> ALTER SESSION SET NLS_NUMERIC_CHARACTERS='.,';
Session wurde geändert.

Enter the SELECT statement shown in Example 3–9:
SQL> SELECT last_name, hire_date, ROUND(salary/8,2) salary FROM employees;

You should see results similar to the following output:
LAST_NAME
------------------------Sciarra
Urman
Popp

HIRE_DATE
SALARY
--------- ---------30.SEP.97
962.5
07.MÄR.98
975
07.DEZ.99
862.5

Note that the language of the month abbreviations is German and the decimal
character is a period.
The behavior of the NLS_LANG environment variable implicitly determines the
language environment of the database for each session. When a session connects to a
database, an ALTER SESSION statement is automatically executed to set the values of
the database parameters NLS_LANGUAGE and NLS_TERRITORY to those specified by
the language and territory arguments of NLS_LANG. If NLS_LANG is not defined,
then no implicit ALTER SESSION statement is executed.
When NLS_LANG is defined, the implicit ALTER SESSION is executed for all instances
to which the session connects, for both direct and indirect connections. If the values of
NLS parameters are changed explicitly with ALTER SESSION during a session, then
the changes are propagated to all instances to which that user session is connected.

3-14 Oracle Database Globalization Support Guide

Date and Time Parameters

Date and Time Parameters
Oracle Database enables you to control the display of date and time. This section
contains the following topics:
■

Date Formats

■

Time Formats

Date Formats
Different date formats are shown in Table 3–4.
Table 3–4

Date Formats

Country

Description

Example

Estonia

dd.mm.yyyy

28.02.2003

Germany

dd-mm-rr

28-02-03

Japan

rr-mm-dd

03-02-28

dd-mon-rr

28-Feb-03

dd-mon-rr

28-Feb-03

This section includes the following parameters:
■

NLS_DATE_FORMAT

■

NLS_DATE_LANGUAGE

NLS_DATE_FORMAT
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, and ALTER
SESSION

Default value

Derived from NLS_TERRITORY

Range of values

Any valid date format mask

The NLS_DATE_FORMAT parameter defines the default date format to use with the
TO_CHAR and TO_DATE functions. The NLS_TERRITORY parameter determines the
default value of NLS_DATE_FORMAT. The value of NLS_DATE_FORMAT can be any
valid date format mask. For example:
NLS_DATE_FORMAT = "MM/DD/YYYY"

To add string literals to the date format, enclose the string literal with double quotes.
Note that when double quotes are included in the date format, the entire value must
be enclosed by single quotes. For example:
NLS_DATE_FORMAT = '"Date: "MM/DD/YYYY'
Example 3–11

Setting the Date Format to Display Roman Numerals

To set the default date format to display Roman numerals for the month, include the
following line in the initialization parameter file:
NLS_DATE_FORMAT = "DD RM YYYY"

Setting Up a Globalization Support Environment

3-15

Date and Time Parameters

Enter the following SELECT statement:
SELECT TO_CHAR(SYSDATE) currdate FROM DUAL;

You should see the following output if today's date is February 12, 1997:
CURRDATE
--------12 II 1997

The value of NLS_DATE_FORMAT is stored in the internal date format. Each format
element occupies two bytes, and each string occupies the number of bytes in the string
plus a terminator byte. Also, the entire format mask has a two-byte terminator. For
example, "MM/DD/YY" occupies 14 bytes internally because there are three format
elements (month, day, and year), two 3-byte strings (the two slashes), and the two-byte
terminator for the format mask. The format for the value of NLS_DATE_FORMAT
cannot exceed 24 bytes.
You can alter the default value of NLS_DATE_FORMAT by:
■

■

Changing its value in the initialization parameter file and then restarting the
instance
Using an ALTER SESSION SET NLS_DATE_FORMAT statement
Oracle Database SQL Reference for more information
about date format elements and the ALTER SESSION statement

See Also:

If a table or index is partitioned on a date column, and if the date format specified by
NLS_DATE_FORMAT does not specify the first two digits of the year, then you must use
the TO_DATE function with a 4-character format mask for the year.
For example:
TO_DATE('11-jan-1997', 'dd-mon-yyyy')

Oracle Database SQL Reference for more information
about partitioning tables and indexes and using TO_DATE

See Also:

NLS_DATE_LANGUAGE
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, ALTER SESSION,
and SQL functions

Default value

Derived from NLS_LANGUAGE

Range of values

Any valid language name

The NLS_DATE_LANGUAGE parameter specifies the language for the day and month
names produced by the TO_CHAR and TO_DATE functions. NLS_DATE_LANGUAGE
overrides the language that is specified implicitly by NLS_LANGUAGE. NLS_DATE_
LANGUAGE has the same syntax as the NLS_LANGUAGE parameter, and all supported
languages are valid values.
NLS_DATE_LANGUAGE also determines the language used for:
■

Month and day abbreviations returned by the TO_CHAR and TO_DATE functions

3-16 Oracle Database Globalization Support Guide

Date and Time Parameters

■

Month and day abbreviations used by the default date format (NLS_DATE_
FORMAT)
Abbreviations for AM, PM, AD, and BC

Example 3–12

NLS_DATE_LANGUAGE=FRENCH, Month and Day Names

As an example of how to use NLS_DATE_LANGUAGE, set the date language to French:
ALTER SESSION SET NLS_DATE_LANGUAGE = FRENCH;

Enter a SELECT statement:
SELECT TO_CHAR(SYSDATE, 'Day:Dd Month yyyy') FROM DUAL;

You should see results similar to the following output:
TO_CHAR(SYSDATE,'DAY:DDMONTHYYYY')
-----------------------------------------------------------Vendredi:07 Décembre 2001

When numbers are spelled in words using the TO_CHAR function, the English spelling
is always used. For example, enter the following SELECT statement:
SQL> SELECT TO_CHAR(TO_DATE('12-Oct.-2001'),'Day: ddspth Month') FROM DUAL;

You should see results similar to the following output:
TO_CHAR(TO_DATE('12-OCT.-2001'),'DAY:DDSPTHMONTH')
-------------------------------------------------------------------Vendredi: twelfth Octobre
Example 3–13

NLS_DATE_LANGUAGE=FRENCH, Month and Day Abbreviations

Month and day abbreviations are determined by NLS_DATE_LANGUAGE. Enter the
following SELECT statement:
SELECT TO_CHAR(SYSDATE, 'Dy:dd Mon yyyy') FROM DUAL;

You should see results similar to the following output:
TO_CHAR(SYSDATE,'DY:DDMO
-----------------------Ve:07 Déc. 2001
Example 3–14

NLS_DATE_LANGUAGE=FRENCH, Default Date Format

The default date format uses the month abbreviations determined by NLS_DATE_
LANGUAGE. For example, if the default date format is DD-MON-YYYY, then insert a date
as follows:
INSERT INTO tablename VALUES ('12-Févr.-1997');

See Also:

Oracle Database SQL Reference

Time Formats
Different time formats are shown in Table 3–5.
Table 3–5

Time Formats

Country

Description

Example

Estonia

hh24:mi:ss

13:50:23

Setting Up a Globalization Support Environment

3-17

Date and Time Parameters

Table 3–5 (Cont.) Time Formats
Country

Description

Example

Germany

hh24:mi:ss

13:50:23

Japan

hh24:mi:ss

13:50:23

hh24:mi:ss

13:50:23

hh:mi:ssxff am

1:50:23.555 PM

This section contains information about the following parameters:
■

NLS_TIMESTAMP_FORMAT

■

NLS_TIMESTAMP_TZ_FORMAT
See Also: Chapter 4, "Datetime Datatypes and Time Zone
Support"

NLS_TIMESTAMP_FORMAT
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, and ALTER
SESSION

Default value

Derived from NLS_TERRITORY

Range of values

Any valid datetime format mask

NLS_TIMESTAMP_FORMAT defines the default date format for the TIMESTAMP and
TIMESTAMP WITH LOCAL TIME ZONE datatypes. The following example shows a
value for NLS_TIMESTAMP_FORMAT:
NLS_TIMESTAMP_FORMAT
Example 3–15

= 'YYYY-MM-DD HH:MI:SS.FF'

Timestamp Format

SQL> SELECT TO_TIMESTAMP('11-nov-2000 01:00:00.336', 'dd-mon-yyyy hh:mi:ss.ff')
FROM DUAL;

You should see results similar to the following output:
TO_TIMESTAMP('11-NOV-200001:00:00.336','DD-MON-YYYYHH:MI:SS.FF')
--------------------------------------------------------------------------2000-11-11 01:00:00.336000000

You can specify the value of NLS_TIMESTAMP_FORMAT by setting it in the
initialization parameter file. You can specify its value for a client as a client
environment variable.
You can also alter the value of NLS_TIMESTAMP_FORMAT by:
■

■

Changing its value in the initialization parameter file and then restarting the
instance
Using the ALTER SESSION SET NLS_TIMESTAMP_FORMAT statement
Oracle Database SQL Reference for more information
about the TO_TIMESTAMP function and the ALTER SESSION
statement

See Also:

3-18 Oracle Database Globalization Support Guide

Calendar Definitions

NLS_TIMESTAMP_TZ_FORMAT
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, and ALTER
SESSION

Default value

Derived from NLS_TERRITORY

Range of values

Any valid datetime format mask

NLS_TIMESTAMP_TZ_FORMAT defines the default date format for the TIMESTAMP
and TIMESTAMP WITH LOCAL TIME ZONE datatypes. It is used with the TO_CHAR
and TO_TIMESTAMP_TZ functions.
You can specify the value of NLS_TIMESTAMP_TZ_FORMAT by setting it in the
initialization parameter file. You can specify its value for a client as a client
environment variable.
Example 3–16

Setting NLS_TIMESTAMP_TZ_FORMAT

The format value must be surrounded by quotation marks. For example:
NLS_TIMESTAMP_TZ_FORMAT

= 'YYYY-MM-DD HH:MI:SS.FF TZH:TZM'

The following example of the TO_TIMESTAMP_TZ function uses the format value that
was specified for NLS_TIMESTAMP_TZ_FORMAT:
SQL> SELECT TO_TIMESTAMP_TZ('2000-08-20, 05:00:00.55 America/Los_Angeles',
'yyyy-mm-dd hh:mi:ss.ff TZR') FROM DUAL;

You should see results similar to the following output:
TO_TIMESTAMP_TZ('2000-08-20,05:00:00.55AMERICA/LOS_ANGELES','YYYY-MM-DDHH:M
--------------------------------------------------------------------------2000-08-20 05:00:00.550000000 -07:00

You can change the value of NLS_TIMESTAMP_TZ_FORMAT by:
■

■

Changing its value in the initialization parameter file and then restarting the
instance
Using the ALTER SESSION statement.
See Also:
■

■

Oracle Database SQL Reference for more information about the
TO_TIMESTAMP_TZ function and the ALTER SESSION
statement
"Choosing a Time Zone File" on page 4-15 for more information
about time zones

Calendar Definitions
This section includes the following topics:
■

Calendar Formats

■

NLS_CALENDAR

Setting Up a Globalization Support Environment

3-19

Calendar Definitions

Calendar Formats
The following calendar information is stored for each territory:
■

First Day of the Week

■

First Calendar Week of the Year

■

Number of Days and Months in a Year

■

First Year of Era

First Day of the Week
Some cultures consider Sunday to be the first day of the week. Others consider
Monday to be the first day of the week. A German calendar starts with Monday, as
shown in Table 3–6.
Table 3–6

German Calendar Example: March 1998

The first day of the week is determined by the NLS_TERRITORY parameter.
See Also:

"NLS_TERRITORY" on page 3-11

First Calendar Week of the Year
Some countries use week numbers for scheduling, planning, and bookkeeping. Oracle
Database supports this convention. In the ISO standard, the week number can be
different from the week number of the calendar year. For example, 1st Jan 1988 is in
ISO week number 53 of 1987. An ISO week always starts on a Monday and ends on a
Sunday.
■

■

If January 1 falls on a Friday, Saturday, or Sunday, then the ISO week that includes
January 1 is the last week of the previous year, because most of the days in the
week belong to the previous year.
If January 1 falls on a Monday, Tuesday, Wednesday, or Thursday, then the ISO
week is the first week of the new year, because most of the days in the week
belong to the new year.

To support the ISO standard, Oracle Database provides the IW date format element. It
returns the ISO week number.
Table 3–7 shows an example in which January 1 occurs in a week that has four or more
days in the first calendar week of the year. The week containing January 1 is the first
ISO week of 1998.
Table 3–7

First ISO Week of the Year: Example 1, January 1998

ISO Week

First ISO week of 1998

3-20 Oracle Database Globalization Support Guide

Calendar Definitions

Table 3–7 (Cont.) First ISO Week of the Year: Example 1, January 1998
Mo

ISO Week

Second ISO week of 1998

Third ISO week of 1998

Fourth ISO week of 1998

Fifth ISO week of 1998

Table 3–8 shows an example in which January 1 occurs in a week that has three or
fewer days in the first calendar week of the year. The week containing January 1 is the
53rd ISO week of 1998, and the following week is the first ISO week of 1999.
Table 3–8

First ISO Week of the Year: Example 2, January 1999

ISO Week

Fifty-third ISO week of 1998

First ISO week of 1999

Second ISO week of 1999

Third ISO week of 1999

Fourth ISO week of 1999

The first calendar week of the year is determined by the NLS_TERRITORY parameter.
See Also:

"NLS_TERRITORY" on page 3-11

Number of Days and Months in a Year
Oracle Database supports six calendar systems in addition to Gregorian, the default:
■

■

Japanese Imperial—uses the same number of months and days as Gregorian, but
the year starts with the beginning of each Imperial Era
ROC Official—uses the same number of months and days as Gregorian, but the
year starts with the founding of the Republic of China
Persian—has 31 days for each of the first six months. The next five months have 30
days each. The last month has either 29 days or 30 days (leap year).

■

Thai Buddha—uses a Buddhist calendar

■

Arabic Hijrah—has 12 months with 354 or 355 days

■

English Hijrah—has 12 months with 354 or 355 days

The calendar system is specified by the NLS_CALENDAR parameter.
See Also:

"NLS_CALENDAR" on page 3-22

First Year of Era
The Islamic calendar starts from the year of the Hegira.
The Japanese Imperial calendar starts from the beginning of an Emperor's reign. For
example, 1998 is the tenth year of the Heisei era. It should be noted, however, that the
Gregorian system is also widely understood in Japan, so both 98 and Heisei 10 can be
used to represent 1998.

Setting Up a Globalization Support Environment

3-21

Numeric and List Parameters

NLS_CALENDAR
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, ALTER SESSION,
and SQL functions

Default value

Gregorian

Range of values

Any valid calendar format name

Many different calendar systems are in use throughout the world. NLS_CALENDAR
specifies which calendar system Oracle Database uses.
NLS_CALENDAR can have one of the following values:
■

Arabic Hijrah

■

English Hijrah

■

Gregorian

■

Japanese Imperial

■

Persian

■

ROC Official (Republic of China)

■

Thai Buddha
See Also: Appendix A, "Locale Data" for a list of calendar
systems, their default date formats, and the character sets in which
dates are displayed

Example 3–17

NLS_CALENDAR='English Hijrah'

Set NLS_CALENDAR to English Hijrah.
SQL> ALTER SESSION SET NLS_CALENDAR='English Hijrah';

Enter a SELECT statement to display SYSDATE:
SELECT SYSDATE FROM DUAL;

You should see results similar to the following output:
SYSDATE
-------------------24 Ramadan
1422

Numeric and List Parameters
This section includes the following topics:
■

Numeric Formats

■

NLS_NUMERIC_CHARACTERS

■

NLS_LIST_SEPARATOR

3-22 Oracle Database Globalization Support Guide

Numeric and List Parameters

Numeric Formats
The database must know the number-formatting convention used in each session to
interpret numeric strings correctly. For example, the database needs to know whether
numbers are entered with a period or a comma as the decimal character (234.00 or
234,00). Similarly, applications must be able to display numeric information in the
format expected at the client site.
Examples of numeric formats are shown in Table 3–9.
Table 3–9

Examples of Numeric Formats

Country

Numeric Formats

Estonia

1 234 567,89

Germany

1.234.567,89

Japan

1,234,567.89

Numeric formats are derived from the setting of the NLS_TERRITORY parameter, but
they can be overridden by the NLS_NUMERIC_CHARACTERS parameter.
See Also:

"NLS_TERRITORY" on page 3-11

NLS_NUMERIC_CHARACTERS
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, ALTER SESSION,
and SQL functions

Default value

Default decimal character and group separator for a particular
territory

Range of values

Any two valid numeric characters

This parameter specifies the decimal character and group separator. The group
separator is the character that separates integer groups to show thousands and
millions, for example. The group separator is the character returned by the G number
format mask. The decimal character separates the integer and decimal parts of a
number. Setting NLS_NUMERIC_CHARACTERS overrides the values derived from the
setting of NLS_TERRITORY.
Any character can be the decimal character or group separator. The two characters
specified must be single-byte, and the characters must be different from each other.
The characters cannot be any numeric character or any of the following characters:
plus (+), hyphen (-), less than sign (<), greater than sign (>). Either character can be a
space.
Example 3–18

Setting NLS_NUMERIC_CHARACTERS

To set the decimal character to a comma and the grouping separator to a period, define
NLS_NUMERIC_CHARACTERS as follows:
ALTER SESSION SET NLS_NUMERIC_CHARACTERS = ",.";

Setting Up a Globalization Support Environment

3-23

Monetary Parameters

SQL statements can include numbers represented as numeric or text literals. Numeric
literals are not enclosed in quotes. They are part of the SQL language syntax and
always use a dot as the decimal character and never contain a group separator. Text
literals are enclosed in single quotes. They are implicitly or explicitly converted to
numbers, if required, according to the current NLS settings.
The following SELECT statement formats the number 4000 with the decimal character
and group separator specified in the ALTER SESSION statement:
SELECT TO_CHAR(4000, '9G999D99') FROM DUAL;

You should see results similar to the following output:
TO_CHAR(4
--------4.000,00

You can change the default value of NLS_NUMERIC_CHARACTERS by:
■

■

Changing the value of NLS_NUMERIC_CHARACTERS in the initialization
parameter file and then restarting the instance
Using the ALTER SESSION statement to change the parameter's value during a
session
Oracle Database SQL Reference for more information
about the ALTER SESSION statement

See Also:

NLS_LIST_SEPARATOR
Property

Description

Parameter type

String

Parameter scope

Environment variable

Default value

Derived from NLS_TERRITORY

Range of values

Any valid character

NLS_LIST_SEPARATOR specifies the character to use to separate values in a list of
values (usually , or . or ; or :). Its default value is derived from the value of NLS_
TERRITORY. For example, a list of numbers from 1 to 5 can be expressed as 1,2,3,4,5 or
1.2.3.4.5 or 1;2;3;4;5 or 1:2:3:4:5.
The character specified must be single-byte and cannot be the same as either the
numeric or monetary decimal character, any numeric character, or any of the following
characters: plus (+), hyphen (-), less than sign (<), greater than sign (>), period (.).

Monetary Parameters
This section includes the following topics:
■

Currency Formats

■

NLS_CURRENCY

■

NLS_ISO_CURRENCY

■

NLS_DUAL_CURRENCY

3-24 Oracle Database Globalization Support Guide

Monetary Parameters

■

NLS_MONETARY_CHARACTERS

■

NLS_CREDIT

■

NLS_DEBIT

Currency Formats
Different currency formats are used throughout the world. Some typical ones are
shown in Table 3–10.
Table 3–10

Currency Format Examples

Country

Example

Estonia

1 234,56 kr

Germany

1.234,56€

Japan

¥1,234.56

£1,234.56

$1,234.56

NLS_CURRENCY
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, ALTER SESSION,
and SQL functions

Default value

Derived from NLS_TERRITORY

Range of values

Any valid currency symbol string

NLS_CURRENCY specifies the character string returned by the L number format mask,
the local currency symbol. Setting NLS_CURRENCY overrides the setting defined
implicitly by NLS_TERRITORY.
Example 3–19

Displaying the Local Currency Symbol

Connect to the sample order entry schema:
SQL> connect oe/oe
Connected.

Enter a SELECT statement similar to the following example:
SQL> SELECT TO_CHAR(order_total, 'L099G999D99') "total" FROM orders
WHERE order_id > 2450;

You should see results similar to the following output:
total
--------------------$078,279.60
$006,653.40
$014,087.50
$010,474.60
$012,589.00
$000,129.00

Setting Up a Globalization Support Environment

3-25

Monetary Parameters

$003,878.40
$021,586.20

You can change the default value of NLS_CURRENCY by:
■

■

Changing its value in the initialization parameter file and then restarting the
instance
Using an ALTER SESSION statement
Oracle Database SQL Reference for more information
about the ALTER SESSION statement

See Also:

NLS_ISO_CURRENCY
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, ALTER SESSION,
and SQL functions

Default value

Derived from NLS_TERRITORY

Range of values

Any valid string

NLS_ISO_CURRENCY specifies the character string returned by the C number format
mask, the ISO currency symbol. Setting NLS_ISO_CURRENCY overrides the value
defined implicitly by NLS_TERRITORY.
Local currency symbols can be ambiguous. For example, a dollar sign ($) can refer to
US dollars or Australian dollars. ISO specifications define unique currency symbols for
specific territories or countries. For example, the ISO currency symbol for the US
dollar is USD. The ISO currency symbol for the Australian dollar is AUD.
More ISO currency symbols are shown in Table 3–11.
Table 3–11

ISO Currency Examples

Country

Example

Estonia

1 234 567,89 EEK

Germany

1.234.567,89 EUR

Japan

1,234,567.89 JPY

1,234,567.89 GBP

1,234,567.89 USD

NLS_ISO_CURRENCY has the same syntax as the NLS_TERRITORY parameter, and all
supported territories are valid values.
Example 3–20

Setting NLS_ISO_CURRENCY

This example assumes that you are connected as oe/oe in the sample schema.
To specify the ISO currency symbol for France, set NLS_ISO_CURRENCY as follows:
ALTER SESSION SET NLS_ISO_CURRENCY = FRANCE;

Enter a SELECT statement:

3-26 Oracle Database Globalization Support Guide

Monetary Parameters

SQL> SELECT TO_CHAR(order_total, 'C099G999D99') "TOTAL" FROM orders
WHERE customer_id = 146;

You should see results similar to the following output:
TOTAL
-----------------EUR017,848.20
EUR027,455.30
EUR029,249.10
EUR013,824.00
EUR000,086.00

You can change the default value of NLS_ISO_CURRENCY by:
■

■

See Also:

NLS_DUAL_CURRENCY
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environmental variable, ALTER SESSION,
and SQL functions

Default value

Derived from NLS_TERRITORY

Range of values

Any valid symbol

Use NLS_DUAL_CURRENCY to override the default dual currency symbol defined
implicitly by NLS_TERRITORY.
NLS_DUAL_CURRENCY was introduced to support the euro currency symbol during
the euro transition period. See Table A–8, " Character Sets that Support the Euro
Symbol" for the character sets that support the euro symbol.

Oracle Database Support for the Euro
Twelve members of the European Monetary Union (EMU) have adopted the euro as
their currency. Setting NLS_TERRITORY to correspond to a country in the EMU
(Austria, Belgium, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the
Netherlands, Portugal, and Spain) results in the default values for NLS_CURRENCY
and NLS_DUAL_CURRENCY being set to EUR.
During the transition period (1999 through 2001), Oracle Database support for the euro
was provided in Oracle Database 8i and later as follows:
■

NLS_CURRENCY was defined as the primary currency of the country

■

NLS_ISO_CURRENCY was defined as the ISO currency code of a given territory

■

NLS_DUAL_CURRENCY was defined as the secondary currency symbol (usually the
euro) for a given territory

Setting Up a Globalization Support Environment

3-27

Monetary Parameters

Beginning with Oracle Database 9i Release 2, the value of NLS_ISO_CURRENCY results
in the ISO currency symbol being set to EUR for EMU member countries who use the
euro. For example, suppose NLS_ISO_CURRENCY is set to FRANCE. Enter the
following SELECT statement:
SELECT TO_CHAR(order_total, 'C099G999D99') "TOTAL" FROM orders
WHERE customer_id=116;

You should see results similar to the following output:
TOTAL
------EUR006,394.80
EUR011,097.40
EUR014,685.80
EUR000,129.00

Customers who must retain their obsolete local currency symbol can override the
default for NLS_DUAL_CURRENCY or NLS_CURRENCY by defining them as parameters
in the initialization file on the server and as environment variables on the client.
Note: NLS_LANG must also be set on the client for NLS_
CURRENCY or NLS_DUAL_CURRENCY to take effect.

It is not possible to override the ISO currency symbol that results from the value of
NLS_ISO_CURRENCY.

NLS_MONETARY_CHARACTERS
Property

Description

Parameter type

String

Parameter scope

Environment variable

Default value

Derived from NLS_TERRITORY

Range of values

Any valid character

NLS_MONETARY_CHARACTERS specifies the character that separates groups of
numbers in monetary expressions. For example, when the territory is America, the
thousands separator is a comma, and the decimal separator is a period.

NLS_CREDIT
Property

Description

Parameter type

String

Parameter scope

Environment variable

Default value

Derived from NLS_TERRITORY

Range of values

Any string, maximum of 9 bytes (not including null)

NLS_CREDIT sets the symbol that displays a credit in financial reports. The default
value of this parameter is determined by NLS_TERRITORY. For example, a space is a
valid value of NLS_CREDIT.
3-28 Oracle Database Globalization Support Guide

Linguistic Sort Parameters

This parameter can be specified only in the client environment.
It can be retrieved through the OCIGetNlsInfo() function.

NLS_DEBIT
Property

Description

Parameter type

String

Parameter scope

Environment variable

Default value

Derived from NLS_TERRITORY

Range of values

Any string, maximum or 9 bytes (not including null)

NLS_DEBIT sets the symbol that displays a debit in financial reports. The default
value of this parameter is determined by NLS_TERRITORY. For example, a minus sign
(-) is a valid value of NLS_DEBIT.
This parameter can be specified only in the client environment.
It can be retrieved through the OCIGetNlsInfo() function.

Linguistic Sort Parameters
You can choose how to sort data by using linguistic sort parameters.
This section includes the following topics:
■

NLS_SORT

■

NLS_COMP
See Also:

Chapter 5, "Linguistic Sorting and String Searching"

NLS_SORT
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, ALTER SESSION,
and SQL functions

Default value

Derived from NLS_LANGUAGE

Range of values

BINARY or any valid linguistic sort name

NLS_SORT specifies the type of sort for character data. It overrides the default value
that is derived from NLS_LANGUAGE.
NLS_SORT contains either of the following values:
NLS_SORT = BINARY | sort_name

BINARY specifies a binary sort. sort_name specifies a linguistic sort sequence.
Example 3–21

Setting NLS_SORT

To specify the German linguistic sort sequence, set NLS_SORT as follows:

Setting Up a Globalization Support Environment

3-29

Linguistic Sort Parameters

NLS_SORT = German

When the NLS_SORT parameter is set to BINARY, the
optimizer can, in some cases, satisfy the ORDER BY clause without
doing a sort by choosing an index scan.

Note:

When NLS_SORT is set to a linguistic sort, a sort is needed to satisfy
the ORDER BY clause if there is no linguistic index for the linguistic
sort specified by NLS_SORT.
If a linguistic index exists for the linguistic sort specified by NLS_
SORT, then the optimizer can, in some cases, satisfy the ORDER BY
clause without doing a sort by choosing an index scan.
You can alter the default value of NLS_SORT by:
■

■

Changing its value in the initialization parameter file and then restarting the
instance
Using an ALTER SESSION statement
See Also:
■
■

■

Chapter 5, "Linguistic Sorting and String Searching"
Oracle Database SQL Reference for more information about the
ALTER SESSION statement
"Linguistic Sorts" on page A-19 for a list of linguistic sort names

NLS_COMP
Property

Description

Parameter type

String

Parameter scope

Initialization parameter, environment variable, and ALTER
SESSION

Default value

BINARY

Range of values

BINARY , LINGUISTIC, or ANSI

The value of NLS_COMP affects the comparison behavior of SQL operations.
You can use NLS_COMP to avoid the cumbersome process of using the NLSSORT
function in SQL statements when you want to perform a linguistic comparison instead
of a binary comparison. When NLS_COMP is set to LINGUISTIC, SQL operations
perform a linguistic comparison based on the value of NLS_SORT. A setting of ANSI is
for backward compatibility; in general, you should set NLS_COMP to LINGUISTIC
when you want to perform a linguistic comparison.
Set NLS_COMP to LINGUISTIC as follows:
ALTER SESSION SET NLS_COMP = LINGUISTIC;

When NLS_COMP is set to LINGUISTIC, a linguistic index improves the performance
of the linguistic comparison. To enable a linguistic index, use the following syntax:
CREATE INDEX i ON t(NLSSORT(col, 'NLS_SORT=FRENCH'));

3-30 Oracle Database Globalization Support Guide

Length Semantics

See Also:
■

"Using Linguistic Sorts" on page 5-2

■

"Using Linguistic Indexes" on page 5-17

Character Set Conversion Parameter
This section includes the following topic:
■

NLS_NCHAR_CONV_EXCP

NLS_NCHAR_CONV_EXCP
Property

Description

Parameter type

String

Parameter scope

Initialization parameter and ALTER SESSION

Default value

FALSE

Range of values

TRUE or FALSE

NLS_NCHAR_CONV_EXCP determines whether an error is reported when there is data
loss during an implicit or explicit character type conversion between
NCHAR/NVARCHAR data and CHAR/VARCHAR2 data. The default value results in no
error being reported.
See Also: Chapter 11, "Character Set Migration" for more
information about data loss during character set conversion

Length Semantics
This section includes the following topic:
■

NLS_LENGTH_SEMANTICS

NLS_LENGTH_SEMANTICS
Property

Description

Parameter type

String

Parameter scope

Environment variable, initialization parameter, and ALTER
SESSION

Default value

BYTE

Range of values

BYTE or CHAR

By default, the character datatypes CHAR and VARCHAR2 are specified in bytes, not
characters. Hence, the specification CHAR(20) in a table definition allows 20 bytes for
storing character data.
This works well if the database character set uses a single-byte character encoding
scheme because the number of characters is the same as the number of bytes. If the
database character set uses a multibyte character encoding scheme, then the number of
bytes no longer equals the number of characters because a character can consist of one

Setting Up a Globalization Support Environment

3-31

Length Semantics

or more bytes. Thus, column widths must be chosen with care to allow for the
maximum possible number of bytes for a given number of characters. You can
overcome this problem by switching to character semantics when defining the column
size.
NLS_LENGTH_SEMANTICS enables you to create CHAR, VARCHAR2, and LONG columns
using either byte or character length semantics. NCHAR, NVARCHAR2, CLOB, and NCLOB
columns are always character-based. Existing columns are not affected.
You may be required to use byte semantics in order to maintain compatibility with
existing applications.
NLS_LENGTH_SEMANTICS does not apply to tables in SYS and SYSTEM. The data
dictionary always uses byte semantics.
Note that if the NLS_LENGTH_SEMANTICS environment variable is not set on the
client, then the client session defaults to the value for NLS_LENGTH_SEMANTICS on
the database server. This enables all client sessions on the network to have the same
NLS_LENGTH_SEMANTICS behavior. Setting the environment variable on an
individual client enables the server initialization parameter to be overridden for that
client.
See Also:
■
■

"Length Semantics" on page 2-8
Oracle Database Concepts for more information about length
semantics

3-32 Oracle Database Globalization Support Guide

4
Datetime Datatypes and Time Zone Support
This chapter includes the following topics:
■

Overview of Datetime and Interval Datatypes and Time Zone Support

■

Datetime and Interval Datatypes

■

Datetime and Interval Arithmetic and Comparisons

■

Datetime SQL Functions

■

Datetime and Time Zone Parameters and Environment Variables

■

Choosing a Time Zone File

■

Upgrading the Time Zone File

■

Setting the Database Time Zone

■

Setting the Session Time Zone

■

Converting Time Zones With the AT TIME ZONE Clause

■

Support for Daylight Saving Time

Overview of Datetime and Interval Datatypes and Time Zone Support
Businesses conduct transactions across different time zones. Oracle Database datetime
and interval datatypes and time zone support make it possible to store consistent
information about the time of events and transactions.
This chapter describes Oracle Database datetime and
interval datatypes. It does not attempt to describe ANSI datatypes
or other kinds of datatypes except when noted.

Note:

Datetime and Interval Datatypes
The datetime datatypes are DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, and
TIMESTAMP WITH LOCAL TIME ZONE. Values of datetime datatypes are sometimes
called datetimes.
The interval datatypes are INTERVAL YEAR TO MONTH and INTERVAL DAY TO
SECOND. Values of interval datatypes are sometimes called intervals.
Both datetimes and intervals are made up of fields. The values of these fields
determine the value of the datatype. The fields that apply to all Oracle Database
datetime and interval datatypes are:

Datetime Datatypes and Time Zone Support

4-1

Datetime and Interval Datatypes

■

YEAR

■

MONTH

■

DAY

■

HOUR

■

MINUTE

■

SECOND

TIMESTAMP WITH TIME ZONE also includes these fields:
■

TIMEZONE_HOUR

■

TIMEZONE_MINUTE

■

TIMEZONE_REGION

■

TIMEZONE_ABBR

TIMESTAMP WITH LOCAL TIME ZONE does not store time zone information
internally, but you can see local time zone information in SQL output if the TZH:TZM
or TZR TZD format elements are specified.
The following sections describe the datetime datatypes and interval datatypes in more
detail:
■

Datetime Datatypes

■

Interval Datatypes
Oracle Database SQL Reference for the valid values of the
datetime and interval fields. Oracle Database SQL Reference also
contains information about format elements.

See Also:

Datetime Datatypes
This section includes the following topics:
■

DATE Datatype

■

TIMESTAMP Datatype

■

TIMESTAMP WITH TIME ZONE Datatype

■

TIMESTAMP WITH LOCAL TIME ZONE Datatype

■

Inserting Values into Datetime Datatypes

■

Choosing a TIMESTAMP Datatype

DATE Datatype
The DATE datatype stores date and time information. Although date and time
information can be represented in both character and number datatypes, the DATE
datatype has special associated properties. For each DATE value, Oracle Database
stores the following information: century, year, month, date, hour, minute, and second.
You can specify a date value by:
■
■

Specifying the date value as a literal
Converting a character or numeric value to a date value with the TO_DATE
function

A date can be specified as an ANSI date literal or as an Oracle Database date value.

4-2 Oracle Database Globalization Support Guide

Datetime and Interval Datatypes

An ANSI date literal contains no time portion and must be specified in exactly the
following format:
DATE 'YYYY-MM-DD'

The following is an example of an ANSI date literal:
DATE '1998-12-25'

Alternatively, you can specify an Oracle Database date value as shown in the following
example:
TO_DATE('1998-DEC-25 17:30','YYYY-MON-DD HH24:MI','NLS_DATE_LANGUAGE=AMERICAN')

The default date format for an Oracle Database date value is derived from the NLS_
DATE_FORMAT and NLS_DATE_LANGUAGE initialization parameters. The date format
in the example includes a two-digit number for the day of the month, an abbreviation
of the month name, the last two digits of the year, and a 24-hour time designation. The
specification for NLS_DATE_LANGUAGE is included because 'DEC' is not a valid value
for MON in all locales.
Oracle Database automatically converts character values that are in the default date
format into date values when they are used in date expressions.
If you specify a date value without a time component, then the default time is
midnight. If you specify a date value without a date, then the default date is the first
day of the current month.
Oracle Database DATE columns always contain fields for both date and time. If your
queries use a date format without a time portion, then you must ensure that the time
fields in the DATE column are set to midnight. You can use the TRUNC (date) SQL
function to ensure that the time fields are set to midnight, or you can make the query a
test of greater than or less than (<, <=, >=, or >) instead of equality or inequality (= or
!=). Otherwise, Oracle Database may not return the query results you expect.
See Also:
■

Oracle Database SQL Reference for more information about the
DATE datatype

■

"NLS_DATE_FORMAT" on page 3-15

■

"NLS_DATE_LANGUAGE" on page 3-16

■

Oracle Database SQL Reference for more information about
literals, format elements such as MM, and the TO_DATE function

TIMESTAMP Datatype
The TIMESTAMP datatype is an extension of the DATE datatype. It stores year, month,
day, hour, minute, and second values. It also stores fractional seconds, which are not
stored by the DATE datatype.
Specify the TIMESTAMP datatype as follows:
TIMESTAMP [(fractional_seconds_precision)]

fractional_seconds_precision is optional and specifies the number of digits in
the fractional part of the SECOND datetime field. It can be a number in the range 0 to 9.
The default is 6.
For example, '26-JUN-02 09:39:16.78' shows 16.78 seconds. The fractional
seconds precision is 2 because there are 2 digits in '78'.

Datetime Datatypes and Time Zone Support

4-3

Datetime and Interval Datatypes

You can specify the TIMESTAMP literal in a format like the following:
TIMESTAMP 'YYYY-MM-DD HH24:MI:SS.FF'

Using the example format, specify TIMESTAMP as a literal as follows:
TIMESTAMP '1997-01-31 09:26:50.12'

The value of NLS_TIMESTAMP_FORMAT initialization parameter determines the
timestamp format when a character string is converted to the TIMESTAMP datatype.
NLS_DATE_LANGUAGE determines the language used for character data such as MON.
See Also:
■

Oracle Database SQL Reference for more information about the
TIMESTAMP datatype

■

"NLS_TIMESTAMP_FORMAT" on page 3-18

■

"NLS_DATE_LANGUAGE" on page 3-16

TIMESTAMP WITH TIME ZONE Datatype
TIMESTAMP WITH TIME ZONE is a variant of TIMESTAMP that includes a time zone
region name or time zone offset in its value. The time zone offset is the difference (in
hours and minutes) between local time and UTC (Coordinated Universal Time,
formerly Greenwich Mean Time). Specify the TIMESTAMP WITH TIME ZONE
datatype as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH TIME ZONE

fractional_seconds_precision is optional and specifies the number of digits in
the fractional part of the SECOND datetime field.
You can specify TIMESTAMP WITH TIME ZONE as a literal as follows:
TIMESTAMP '1997-01-31 09:26:56.66 +02:00'

Two TIMESTAMP WITH TIME ZONE values are considered identical if they represent
the same instant in UTC, regardless of the TIME ZONE offsets stored in the data. For
example, the following expressions have the same value:
TIMESTAMP '1999-01-15 8:00:00 -8:00'
TIMESTAMP '1999-01-15 11:00:00 -5:00'

You can replace the UTC offset with the TZR (time zone region) format element. The
following expression specifies US/Pacific for the time zone region:
TIMESTAMP '1999-01-15 8:00:00 US/Pacific'

To eliminate the ambiguity of boundary cases when the time switches from Standard
Time to Daylight Saving Time, use both the TZR format element and the corresponding
TZD format element. The TZD format element is an abbreviation of the time zone
region with Daylight Saving Time information included. Examples are PST for
US/Pacific standard time and PDT for US/Pacific daylight time. The following
specification ensures that a Daylight Saving Time value is returned:
TIMESTAMP '1999-10-29 01:30:00 US/Pacific PDT'

If you do not add the TZD format element, and the datetime value is ambiguous, then
Oracle Database returns an error if you have the ERROR_ON_OVERLAP_TIME session
parameter set to TRUE. If ERROR_ON_OVERLAP_TIME is set to FALSE (the default
value), then Oracle Database interprets the ambiguous datetime as Standard Time.
4-4 Oracle Database Globalization Support Guide

Datetime and Interval Datatypes

The default date format for the TIMESTAMP WITH TIME ZONE datatype is
determined by the value of the NLS_TIMESTAMP_TZ_FORMAT initialization
parameter.
See Also:
■

■

Oracle Database SQL Reference for more information about the
TIMESTAMP WITH TIME ZONE datatype
"TIMESTAMP Datatype" on page 4-3 for more information
about fractional seconds precision

■

"Support for Daylight Saving Time" on page 4-23

■

"NLS_TIMESTAMP_TZ_FORMAT" on page 3-19

■

Oracle Database SQL Reference for more information about
format elements
Oracle Database SQL Reference for more information about
setting the ERROR_ON_OVERLAP_TIME session parameter

TIMESTAMP WITH LOCAL TIME ZONE Datatype
TIMESTAMP WITH LOCAL TIME ZONE is another variant of TIMESTAMP. It differs
from TIMESTAMP WITH TIME ZONE as follows: data stored in the database is
normalized to the database time zone, and the time zone offset is not stored as part of
the column data. When users retrieve the data, Oracle Database returns it in the users'
local session time zone. The time zone offset is the difference (in hours and minutes)
between local time and UTC (Coordinated Universal Time, formerly Greenwich Mean
Time).
Specify the TIMESTAMP WITH LOCAL TIME ZONE datatype as follows:
TIMESTAMP [(fractional_seconds_precision)] WITH LOCAL TIME ZONE

fractional_seconds_precision is optional and specifies the number of digits in
the fractional part of the SECOND datetime field.
There is no literal for TIMESTAMP WITH LOCAL TIME ZONE, but TIMESTAMP literals
and TIMESTAMP WITH TIME ZONE literals can be inserted into a TIMESTAMP WITH
LOCAL TIME ZONE column.
The default date format for TIMESTAMP WITH LOCAL TIME ZONE is determined by
the value of the NLS_TIMESTAMP_FORMAT initialization parameter.
See Also:
■

■

Oracle Database SQL Reference for more information about the
TIMESTAMP WITH LOCAL TIME ZONE datatype
"TIMESTAMP Datatype" on page 4-3 for more information
about fractional seconds precision
"NLS_TIMESTAMP_FORMAT" on page 3-18

Inserting Values into Datetime Datatypes
You can insert values into a datetime column in the following ways:
■

■

Insert a character string whose format is based on the appropriate NLS format
value
Insert a literal

Datetime Datatypes and Time Zone Support

4-5

Datetime and Interval Datatypes

■

Insert a literal for which implicit conversion is performed

■

Use the TO_TIMESTAMP, TO_TIMESTAMP_TZ, or TO_DATE SQL function

The following examples show how to insert data into datetime datatypes.
Example 4–1 Inserting Data into a DATE Column

Set the date format.
SQL> ALTER SESSION SET NLS_DATE_FORMAT='DD-MON-YYYY HH24:MI:SS';

Create a table table_dt with columns c_id and c_dt. The c_id column is of
NUMBER datatype and helps to identify the method by which the data is entered. The
c_dt column is of DATE datatype.
SQL> CREATE TABLE table_dt (c_id NUMBER, c_dt DATE);

Insert a date as a character string.
SQL> INSERT INTO table_dt VALUES(1, '01-JAN-2003');

Insert the same date as a DATE literal.
SQL> INSERT INTO table_dt VALUES(2, DATE '2003-01-01');

Insert the date as a TIMESTAMP literal. Oracle Database drops the time zone
information.
SQL> INSERT INTO table_dt VALUES(3, TIMESTAMP '2003-01-01 00:00:00 US/Pacific');

Insert the date with the TO_DATE function.
SQL> INSERT INTO table_dt VALUES(4, TO_DATE('01-JAN-2003', 'DD-MON-YYYY'));

Display the data.
SQL> SELECT * FROM table_dt;
C_ID
---------1
2
3
4

C_DT
-------------------01-JAN-2003 00:00:00
01-JAN-2003 00:00:00
01-JAN-2003 00:00:00
01-JAN-2003 00:00:00

Example 4–2 Inserting Data into a TIMESTAMP Column

Set the timestamp format.
SQL> ALTER SESSION SET NLS_TIMESTAMP_FORMAT='DD-MON-YY HH:MI:SSXFF';

Create a table table_ts with columns c_id and c_ts. The c_id column is of
NUMBER datatype and helps to identify the method by which the data is entered. The
c_ts column is of TIMESTAMP datatype.
SQL> CREATE TABLE table_ts(c_id NUMBER, c_ts TIMESTAMP);

Insert a date and time as a character string.
SQL> INSERT INTO table_ts VALUES(1, '01-JAN-2003 2:00:00');

Insert the same date and time as a TIMESTAMP literal.
SQL> INSERT INTO table_ts VALUES(2, TIMESTAMP '2003-01-01 2:00:00');

4-6 Oracle Database Globalization Support Guide

Datetime and Interval Datatypes

Insert the same date and time as a TIMESTAMP WITH TIME ZONE literal. Oracle
Database converts it to a TIMESTAMP value, which means that the time zone
information is dropped.
SQL> INSERT INTO table_ts VALUES(3, TIMESTAMP '2003-01-01 2:00:00 -08:00');

Display the data.
SQL> SELECT * FROM table_ts;
C_ID
---------1
2
3

C_TS
----------------------------01-JAN-03 02:00:00.000000 AM
01-JAN-03 02:00:00.000000 AM
01-JAN-03 02:00:00.000000 AM

Note that the three methods result in the same value being stored.
Example 4–3 Inserting Data into the TIMESTAMP WITH TIME ZONE Datatype

Set the timestamp format.
SQL> ALTER SESSION SET NLS_TIMESTAMP_TZ_FORMAT='DD-MON-RR HH:MI:SSXFF AM TZR';

Set the time zone to '-07:00'.
SQL> ALTER SESSION SET TIME_ZONE='-7:00';

Create a table table_tstz with columns c_id and c_tstz. The c_id column is of
NUMBER datatype and helps to identify the method by which the data is entered. The
c_tstz column is of TIMESTAMP WITH TIME ZONE datatype.
SQL> CREATE TABLE table_tstz (c_id NUMBER, c_tstz TIMESTAMP WITH TIME ZONE);

Insert a date and time as a character string.
SQL> INSERT INTO table_tstz VALUES(1, '01-JAN-2003 2:00:00 AM -07:00');

Insert the same date and time as a TIMESTAMP literal. Oracle Database converts it to a
TIMESTAMP WITH TIME ZONE literal, which means that the session time zone is
appended to the TIMESTAMP value.
SQL> INSERT INTO table_tstz VALUES(2, TIMESTAMP '2003-01-01 2:00:00');

Insert the same date and time as a TIMESTAMP WITH TIME ZONE literal.
SQL> INSERT INTO table_tstz VALUES(3, TIMESTAMP '2003-01-01 2:00:00 -8:00');

Display the data.
SQL> SELECT * FROM table_tstz;
C_ID
---------1
2
3

C_TSTZ
-----------------------------------01-JAN-03 02:00.00:000000 AM -07:00
01-JAN-03 02:00:00.000000 AM -07:00
01-JAN-03 02:00:00.000000 AM -08:00

Note that the time zone is different for method 3, because the time zone information
was specified as part of the TIMESTAMP WITH TIME ZONE literal.

Datetime Datatypes and Time Zone Support

4-7

Datetime and Interval Datatypes

Example 4–4 Inserting Data into the TIMESTAMP WITH LOCAL TIME ZONE Datatype

Consider data that is being entered in Denver, Colorado, U.S.A., whose time zone is
UTC-7.
SQL> ALTER SESSION SET TIME_ZONE='-07:00';

Create a table table_tsltz with columns c_id and c_tsltz. The c_id column is
of NUMBER datatype and helps to identify the method by which the data is entered.
The c_tsltz column is of TIMESTAMP WITH LOCAL TIME ZONE datatype.
SQL> CREATE TABLE table_tsltz (c_id NUMBER, c_tsltz TIMESTAMP WITH LOCAL TIME ZONE);

Insert a date and time as a character string.
SQL> INSERT INTO table_tsltz VALUES(1, '01-JAN-2003 2:00:00');

Insert the same data as a TIMESTAMP WITH LOCAL TIME ZONE literal.
SQL> INSERT INTO table_tsltz VALUES(2, TIMESTAMP '2003-01-01 2:00:00');

Insert the same data as a TIMESTAMP WITH TIME ZONE literal. Oracle Database
converts the data to a TIMESTAMP WITH LOCAL TIME ZONE value. This means the
time zone that is entered (-08:00) is converted to the session time zone value
(-07:00).
SQL> INSERT INTO table_tsltz VALUES(3, TIMESTAMP '2003-01-01 2:00:00 -08:00');

Display the data.
SQL> SELECT * FROM table_tsltz;
C_ID
---------1
2
3

C_TSLTZ
-----------------------------------01-JAN-03 02.00.00.000000 AM
01-JAN-03 02.00.00.000000 AM
01-JAN-03 03.00.00.000000 AM

Note that the information that was entered as UTC-8 has been changed to the local
time zone, changing the hour from 2 to 3.
"Datetime SQL Functions" on page 4-12 for more
information about the TO_TIMESTAMP or TO_TIMESTAMP_TZ SQL
functions

See Also:

Choosing a TIMESTAMP Datatype
Use the TIMESTAMP datatype when you need a datetime value without locale
information. For example, you can store information about the times when workers
punch a timecard in and out of their assembly line workstations. The TIMESTAMP
datatype uses 7 or 11 bytes of storage.
Use the TIMESTAMP WITH TIME ZONE datatype when the application is used across
time zones. Consider a banking company with offices around the world. It records a
deposit to an account at 11 a.m. in London and a withdrawal of the same amount from
the account at 9 a.m. in New York. The money is in the account for three hours. Unless
time zone information is stored with the account transactions, it appears that the
account is overdrawn from 9 a.m. to 11 a.m.
The TIMESTAMP WITH TIME ZONE datatype requires 13 bytes of storage, or two
more bytes of storage than the TIMESTAMP and TIMESTAMP WITH LOCAL TIME
ZONE datatypes because it stores time zone information. The time zone is stored as an

4-8 Oracle Database Globalization Support Guide

Datetime and Interval Datatypes

offset from UTC or as a time zone region name. The data is available for display or
calculations without additional processing. A TIMESTAMP WITH TIME ZONE column
cannot be used as a primary key. If an index is created on a TIMESTAMP WITH TIME
ZONE column, it becomes a function-based index.
The TIMESTAMP WITH LOCAL TIME ZONE datatype stores the timestamp without
time zone information. It normalizes the data to the database time zone every time the
data is sent to and from a client. It requires 11 bytes of storage.
The TIMESTAMP WITH LOCAL TIME ZONE datatype is appropriate when the
original time zone is of no interest, but the relative times of events are important.
Consider the transactions described in the previous banking example. Suppose the
data is recorded using the TIMESTAMP WITH LOCAL TIME ZONE datatype. If the
database time zone of the bank is set to Asia/Hong_Kong, then an employee in Hong
Kong who displays the data would see that the deposit was made at 7 p.m. and the
withdrawal was made at 10 p.m. If the same data is displayed in London, it would
show that the deposit was made at 11 a.m. and the withdrawal was made at 2 p.m. The
three-hour difference is preserved, but the time zone/region of the original transaction
is not. Because of this, the actual time of the transaction can be interpreted differently
depending on the time zone/region from which the information is retrieved. For
example, in London, the transactions appear to be conducted within business hours,
in Hong Kong, they do not.
Note that, because the original time zone region of the time data is not preserved in
the TIMESTAMP WITH LOCAL TIME ZONE data type, time data referring to times from
regions such as Brazil and Israel, regions that update their Daylight Savings Transition
dates frequently and at irregular periods, may be inaccurate. If time information from
these regions is key to your application, you may wish to consider using one of the
other datetime types.

Interval Datatypes
Interval datatypes store time durations. They are used primarily with analytic
functions. For example, you can use them to calculate a moving average of stock
prices. You must use interval datatypes to determine the values that correspond to a
particular percentile. You can also use interval datatypes to update historical tables.
This section includes the following topics:
■

INTERVAL YEAR TO MONTH Datatype

■

INTERVAL DAY TO SECOND Datatype

■

Inserting Values into Interval Datatypes
See Also: Oracle Data Warehousing Guide for more information
about analytic functions, including moving averages and inverse
percentiles

INTERVAL YEAR TO MONTH Datatype
INTERVAL YEAR TO MONTH stores a period of time using the YEAR and MONTH
datetime fields. Specify INTERVAL YEAR TO MONTH as follows:
INTERVAL YEAR [(year_precision)] TO MONTH

year_precision is the number of digits in the YEAR datetime field. Accepted values
are 0 to 9. The default value of year_precision is 2.

Datetime Datatypes and Time Zone Support

4-9

Datetime and Interval Arithmetic and Comparisons

Interval values can be specified as literals. There are many ways to specify interval
literals.The following is one example of specifying an interval of 123 years and 2
months.The year precision is 3.
INTERVAL '123-2' YEAR(3) TO MONTH

Oracle Database SQL Reference for more information
about specifying interval literals with the INTERVAL YEAR TO
MONTH datatype

See Also:

INTERVAL DAY TO SECOND Datatype
INTERVAL DAY TO SECOND stores a period of time in terms of days, hours, minutes,
and seconds. Specify this datatype as follows:
INTERVAL DAY [(day_precision)] TO SECOND [(fractional_seconds_precision)]

day_precision is the number of digits in the DAY datetime field. Accepted values
are 0 to 9. The default is 2.
fractional_seconds_precision is the number of digits in the fractional part of
the SECOND datetime field. Accepted values are 0 to 9. The default is 6.
The following is one example of specifying an interval of 4 days, 5 hours, 12 minutes,
10 seconds, and 222 thousandths of a second. The fractional second precision is 3.
INTERVAL '4 5:12:10.222' DAY TO SECOND(3)

Interval values can be specified as literals. There are many ways to specify interval
literals.
Oracle Database SQL Reference for more information
about specifying interval literals with the INTERVAL DAY TO
SECOND datatype

See Also:

Inserting Values into Interval Datatypes
You can insert values into an interval column in the following ways:
■

Insert an interval as a literal. For example:
INSERT INTO table1 VALUES (INTERVAL '4-2' YEAR TO MONTH);

This statement inserts an interval of 4 years and 2 months.
Oracle Database recognizes literals for other ANSI interval types and converts the
values to Oracle Database interval values.
■

Use the NUMTODSINTERVAL, NUMTOYMINTERVAL, TO_DSINTERVAL, and TO_
YMINTERVAL SQL functions.
See Also:

"Datetime SQL Functions" on page 4-12

Datetime and Interval Arithmetic and Comparisons
This section includes the following topics:
■

Datetime and Interval Arithmetic

■

Datetime Comparisons

■

Explicit Conversion of Datetime Datatypes

4-10 Oracle Database Globalization Support Guide

Datetime and Interval Arithmetic and Comparisons

Datetime and Interval Arithmetic
You can perform arithmetic operations on date (DATE), timestamp (TIMESTAMP,
TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE) and
interval (INTERVAL DAY TO SECOND and INTERVAL YEAR TO MONTH) data. You
can maintain the most precision in arithmetic operations by using a timestamp
datatype with an interval datatype.
You can use NUMBER constants in arithmetic operations on date and timestamp values.
Oracle Database internally converts timestamp values to date values before doing
arithmetic operations on them with NUMBER constants. This means that information
about fractional seconds is lost during operations that include both date and
timestamp values. Oracle Database interprets NUMBER constants in datetime and
interval expressions as number of days.
Each DATE value contains a time component. The result of many date operations
includes a fraction. This fraction means a portion of one day. For example, 1.5 days is
36 hours. These fractions are also returned by Oracle Database built-in SQL functions
for common operations on DATE data. For example, the built-in MONTHS_BETWEEN
SQL function returns the number of months between two dates. The fractional portion
of the result represents that portion of a 31-day month.
Oracle Database performs all timestamp arithmetic in UTC time. For TIMESTAMP
WITH LOCAL TIME ZONE data, Oracle Database converts the datetime value from the
database time zone to UTC and converts back to the database time zone after
performing the arithmetic. For TIMESTAMP WITH TIME ZONE data, the datetime
value is always in UTC, so no conversion is necessary.
See Also:
■

■

Oracle Database SQL Reference for detailed information about
datetime and interval arithmetic operations
"Datetime SQL Functions" on page 4-12 for information about
which functions cause implicit conversion to DATE

Datetime Comparisons
When you compare date and timestamp values, Oracle Database converts the data to
the more precise datatype before doing the comparison. For example, if you compare
data of TIMESTAMP WITH TIME ZONE datatype with data of TIMESTAMP datatype,
Oracle Database converts the TIMESTAMP data to TIMESTAMP WITH TIME ZONE,
using the session time zone.
The order of precedence for converting date and timestamp data is as follows:
1.

DATE

TIMESTAMP

TIMESTAMP WITH LOCAL TIME ZONE

TIMESTAMP WITH TIME ZONE

For any pair of datatypes, Oracle Database converts the datatype that has a smaller
number in the preceding list to the datatype with the larger number.

Explicit Conversion of Datetime Datatypes
If you want to do explicit conversion of datetime datatypes, use the CAST SQL
function. You can explicitly convert DATE, TIMESTAMP, TIMESTAMP WITH TIME
ZONE, and TIMESTAMP WITH LOCAL TIME ZONE to another datatype in the list.
Datetime Datatypes and Time Zone Support 4-11

Datetime SQL Functions

See Also:

Oracle Database SQL Reference

Datetime SQL Functions
Datetime functions operate on date (DATE), timestamp (TIMESTAMP, TIMESTAMP
WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE) and interval
(INTERVAL DAY TO SECOND, INTERVAL YEAR TO MONTH) values.
Some of the datetime functions were designed for the Oracle Database DATE datatype.
If you provide a timestamp value as their argument, then Oracle Database internally
converts the input type to a DATE value. Oracle Database does not perform internal
conversion for the ROUND and TRUNC functions.
Table 4–1 shows the datetime functions that were designed for the Oracle Database
DATE datatype. For more detailed descriptions, refer to Oracle Database SQL Reference.
Table 4–1

Datetime Functions Designed for the DATE Datatype

Function

Description

ADD_MONTHS

Returns the date d plus n months

LAST_DAY

Returns the last day of the month that contains date

MONTHS_BETWEEN

Returns the number of months between date1 and date2

NEW_TIME

Returns the date and time in zone2 time zone when the date
and time in zone1 time zone are date
Note: This function takes as input only a limited number of
time zones. You can have access to a much greater number of
time zones by combining the FROM_TZ function and the
datetime expression.

NEXT_DAY

Returns the date of the first weekday named by char that is
later than date

ROUND (date)

Returns date rounded to the unit specified by the fmt format
model

TRUNC (date)

Returns date with the time portion of the day truncated to the
unit specified by the fmt format model

Table 4–2 describes additional datetime functions. For more detailed descriptions, refer
to Oracle Database SQL Reference.
Table 4–2

Additional Datetime Functions

Datetime Function

Description

CURRENT_DATE

Returns the current date in the session time zone in a value in the
Gregorian calendar, of the DATE datatype

CURRENT_TIMESTAMP

Returns the current date and time in the session time zone as a
TIMESTAMP WITH TIME ZONE value

DBTIMEZONE

Returns the value of the database time zone. The value is a time
zone offset or a time zone region name

EXTRACT (datetime)

Extracts and returns the value of a specified datetime field from a
datetime or interval value expression

FROM_TZ

Converts a TIMESTAMP value at a time zone to a TIMESTAMP
WITH TIME ZONE value

4-12 Oracle Database Globalization Support Guide

Datetime and Time Zone Parameters and Environment Variables

Table 4–2 (Cont.) Additional Datetime Functions
Datetime Function

Description

LOCALTIMESTAMP

Returns the current date and time in the session time zone in a
value of the TIMESTAMP datatype

NUMTODSINTERVAL

Converts number n to an INTERVAL DAY TO SECOND literal

NUMTOYMINTERVAL

Converts number n to an INTERVAL YEAR TO MONTH literal

SESSIONTIMEZONE

Returns the value of the current session's time zone

SYS_EXTRACT_UTC

Extracts the UTC from a datetime with time zone offset

SYSDATE

Returns the date and time of the operating system on which the
database resides, taking into account the time zone of the database
server's operating system that was in effect when the database
was started

SYSTIMESTAMP

Returns the system date, including fractional seconds and time
zone of the system on which the database resides

TO_CHAR (datetime)

Converts a datetime or interval value of DATE, TIMESTAMP,
TIMESTAMP WITH TIME ZONE, or TIMESTAMP WITH LOCAL
TIME ZONE datatype to a value of VARCHAR2 datatype in the
format specified by the fmt date format

TO_DSINTERVAL

Converts a character string of CHAR, VARCHAR2, NCHAR, or
NVARCHAR2 datatype to a value of INTERVAL DAY TO SECOND
datatype

TO_NCHAR (datetime)

Converts a datetime or interval value of DATE, TIMESTAMP,
TIMESTAMP WITH TIME ZONE, TIMESTAMP WITH LOCAL
TIME ZONE, INTERVAL MONTH TO YEAR, or INTERVAL DAY
TO SECOND datatype from the database character set to the
national character set

TO_TIMESTAMP

Converts a character string of CHAR, VARCHAR2, NCHAR, or
NVARCHAR2 datatype to a value of TIMESTAMP datatype

TO_TIMESTAMP_TZ

Converts a character string of CHAR, VARCHAR2, NCHAR, or
NVARCHAR2 datatype to a value of the TIMESTAMP WITH TIME
ZONE datatype

TO_YMINTERVAL

Converts a character string of CHAR, VARCHAR2, NCHAR, or
NVARCHAR2 datatype to a value of the INTERVAL YEAR TO
MONTH datatype

TZ_OFFSET

Returns the time zone offset that corresponds to the entered value,
based on the date that the statement is executed

See Also:

Oracle Database SQL Reference

Datetime and Time Zone Parameters and Environment Variables
This section includes the following topics:
■

Datetime Format Parameters

■

Time Zone Environment Variables

■

Daylight Saving Time Session Parameter

Datetime Format Parameters
Table 4–3 contains the names and descriptions of the datetime format parameters.

Datetime Datatypes and Time Zone Support 4-13

Datetime and Time Zone Parameters and Environment Variables

Table 4–3

Datetime Format Parameters

Parameter

Description

NLS_DATE_FORMAT

Defines the default date format to use with the TO_CHAR and
TO_DATE functions

NLS_TIMESTAMP_FORMAT

Defines the default timestamp format to use with the TO_
CHAR and TO_TIMESTAMP functions

NLS_TIMESTAMP_TZ_FORMAT Defines the default timestamp with time zone format to use
with the TO_CHAR and TO_TIMESTAMP_TZ functions

Their default values are derived from NLS_TERRITORY.
You can specify their values by setting them in the initialization parameter file. You
can specify their values for a client as client environment variables.
You can also change their values by changing their value in the initialization
parameter file and then restarting the instance.
To change their values during a session, use the ALTER SESSION statement.
See Also:
■

"Date and Time Parameters" on page 3-15 for more information,
including examples

■

"NLS_DATE_FORMAT" on page 3-15

■

"NLS_TIMESTAMP_FORMAT" on page 3-18

■

"NLS_TIMESTAMP_TZ_FORMAT" on page 3-19

Time Zone Environment Variables
The time zone environment variables are:
■

■

ORA_TZFILE, which specifies the Oracle Database time zone file used by the
database
ORA_SDTZ, which specifies the default session time zone
See Also:
■

"Choosing a Time Zone File" on page 4-15

■

"Setting the Session Time Zone" on page 4-21

Daylight Saving Time Session Parameter
ERROR_ON_OVERLAP_TIME is a session parameter that determines how Oracle
Database handles an ambiguous datetime boundary value. Ambiguous datetime
values can occur when the time changes between Daylight Saving Time and standard
time.
The possible values are TRUE and FALSE. When ERROR_ON_OVERLAP_TIME is TRUE,
then an error is returned when Oracle Database encounters an ambiguous datetime
value. When ERROR_ON_OVERLAP_TIME is FALSE, then ambiguous datetime values
are assumed to be the standard time representation for the region. The default value is
FALSE.
See Also:

"Support for Daylight Saving Time" on page 4-23

4-14 Oracle Database Globalization Support Guide

Choosing a Time Zone File

Choosing a Time Zone File
The Oracle Database time zone files contain the valid time zone names. The following
information is also included for each time zone:
■

Offset from Coordinated Universal Time (UTC)

■

Transition times for Daylight Saving Time

■

Abbreviations for standard time and Daylight Saving Time

Two time zone files are included in the Oracle Database home directory. The default
time zone file is $ORACLE_HOME/oracore/zoneinfo/timezonelrg.dat, which
contains all the time zones defined in the database. $ORACLE_
HOME/oracore/zoneinfo/timezone.dat contains only the most commonly used
time zones.
If you use the larger time zone file, then you must continue to use it unless you are
sure that none of the additional time zones that it contains are used for data that is
stored in the database. Also, all databases and client installations that share
information must use the same time zone file.
To enable the use of $ORACLE_HOME/oracore/zoneinfo/timezone.dat, or if
you are already using it as your time zone file and you want to continue to do so in an
Oracle Database 11g environment, perform the following steps:
1.

Shut down the database if it has been started.

Set the ORA_TZFILE environment variable to $ORACLE_
HOME/oracore/zoneinfo/timezone.dat.

Restart the database.
If you are already using the default time zone file, then it is
not practical to change to the smaller time zone file because the
database may contain data with time zones that are not part of the
smaller time zone file.

Note:

Oracle Database time zone data is derived from the public domain information
available at ftp://elsie.nci.nih.gov/pub/. Oracle Database time zone data
may not reflect the most recent data available at this site.
You can obtain a list of time zone names and time zone abbreviations from the time
zone file that is installed with your database by entering the following statement:
SELECT tzname, tzabbrev FROM V$TIMEZONE_NAMES;

For the default time zone file, this statement results in output similar to the following:
TZNAME
-------------------Africa/Algiers
Africa/Algiers
Africa/Algiers
Africa/Algiers
Africa/Algiers
Africa/Algiers
Africa/Cairo
Africa/Cairo
Africa/Cairo
Africa/Casablanca

TZABBREV
---------LMT
PMT
WET
WEST
CET
CEST
LMT
EET
EEST
LMT

Datetime Datatypes and Time Zone Support 4-15

Choosing a Time Zone File

Africa/Casablanca
Africa/Casablanca
Africa/Casablanca
...
W-SU
W-SU
W-SU
W-SU
W-SU
W-SU
W-SU
W-SU
W-SU
WET
WET
WET

WET
WEST
CET
LMT
MMT
MST
MDST
S
MSD
MSK
EET
EEST
LMT
WEST
WET

1393 rows selected.

There are 6 time zone abbreviations associated with the Africa/Algiers time zone, 3
abbreviations associated with the Africa/Cairo time zone, and 4 abbreviations
associated with the Africa/Casablanca time zone. The following table shows the time
zone abbreviations and their meanings.
Time Zone Abbreviation

Meaning

LMT

Local Mean Time

PMT

Paris Mean Time

WET

Western European Time

WEST

Western European Summer Time

CET

Central Europe Time

CEST

Central Europe Summer Time

EET

Eastern Europe Time

EEST

Eastern Europe Summer Time

Note that an abbreviation can be associated with more than one time zone. For
example, CET is associated with both Africa/Algiers and Africa/Casablanca, as well
as time zones in Europe.
If you want a list of time zones without repeating the time zone name for each
abbreviation, use the following query:
SELECT UNIQUE tzname FROM V$TIMEZONE_NAMES;

For the default time zone file, this results in output similar to the following:
TZNAME
-------------------Africa/Algiers
Africa/Cairo
Africa/Casablanca
Africa/Ceuta
...
US/Pacific
US/Pacific-New
US/Samoa

4-16 Oracle Database Globalization Support Guide

Upgrading the Time Zone File

UTC
W-SU
WET

The default time zone file contains more than 350 unique time zone names. The small
time zone file contains more than 180 unique time zone names.
See Also:
■
■

"Customizing Time Zone Data" on page 13-15
"Time Zone Names" on page A-23 for a list of valid Oracle
Database time zone names

Upgrading the Time Zone File
The time zone files that are supplied with Oracle Database are updated periodically to
reflect changes in transition rules for various time zone regions. The files supplied
with Oracle Database 11g have been updated to version 3. This version includes the
recent change in the Daylight Savings Time (DST) rule for US time zones starting with
the year 2007.
Note: Oracle Database 9i includes version 1 of the time zone files,
and Oracle Database 10g includes version 2. Various patches and
patch sets, which are released separately for these releases, may
update the time zone file version as well.

DST Transition Rules Changes
The changes to DST transition rules may affect existing data of TIMESTAMP WITH
TIME ZONE datatype, because of the way Oracle Database stores this data internally.
When users enter timestamps with time zone, Oracle Database converts the data to
UTC, based on the transition rules in the time zone file, and stores the data together
with the ID of the original time zone on disk. When data is retrieved, the reverse
conversion from UTC takes place. For example, when the version 2 transition rules
were in effect, the value TIMESTAMP '2007-11-02 12:00:00 America/Los_
Angeles', would have been stored as UTC value '2007-11-02 20:00:00' plus
the time zone ID for 'America/Los_Angeles'. The time in Los Angeles would
have been UTC minus eight hours (PST). Under version 3 of the transition rules, the
offset for the same day is minus seven hours (PDT). Beginning with year 2007, the DST
will be in effect longer (until the first Sunday of November, which is November 4th in
year 2007). Now when users retrieve the same timestamp and the new offset is added
to the stored UTC time, they will receive TIMESTAMP '2007-11-02 13:00:00
America/Los_Angeles'. There is a one hour difference compared to the data
previous to version 3 taking effect.
In the most common case, the value TIMESTAMP '2007-11-02 12:00:00
America/Los_Angeles' is meant to represent noon of November 2nd, 2007 in Los
Angeles. Because the change to the DST transition rules introduces the one hour shift,
the timestamp must be updated to point back to 12:00 p.m., as described further in this
section. In the less common case, the value might be meant to represent the local time
in Los Angeles when it is 08:00 p.m. in UTC. In this less common case, the value
actually becomes correct only after the time zone file has been updated. No further
correction is needed in this case. Therefore, before updating any timestamp values, it is
important to understand what the values are meant to represent.

Datetime Datatypes and Time Zone Support 4-17

Upgrading the Time Zone File

For any time zone region whose transition rules have been
updated, the issue discussed in this section, "Upgrading the Time
Zone File", affects only timestamps that point to the future relative to
the effective date of the corresponding DST rule change. For example,
no timestamp before year 2007 is affected by the version 3 change to
the 'America/Los_Angeles' time zone region.

Note:

Updating the Time Zone File with the utltzuv2.sql Script
You can use the $ORACLE_HOME/rdbms/admin/utltzuv2.sql script to discover
all columns of TIMESTAMP WITH TIME ZONE datatype in your database that are
potentially affected by a time zone file update. The result is stored in the sys.sys_
tzuv2_temptab table, which has five columns: table_owner, table_name,
column_name, rowcount, and nested_tab. Each row of sys.sys_tzuv2_
temptab describes a TIMESTAMP WITH TIME ZONE table column that: (a) contains at
least one timestamp in any of the time zone regions that are affected by the time zone
file update, or (b) belongs to a nested table. The nested_tab value 'YES' indicates
that the table specified in the table_name has been inserted because of condition (b).
For performance reasons, nested table columns are reported without scanning their
contents for the affected time zone regions. For columns inserted because of condition
(a), the rowcount value contains the number of timestamps in the column that
contains one of the affected time zone regions.
The utltzuv2.sql script must be run before you update the database time zone file.
This script identifies the time zone regions to search for by comparing the version of
the current database time zone file with the version of the time zone file for which the
script has been created. If the database time zone file is updated too early, then the
script does nothing, as the two versions are equal. If the time zone file changes as
result of an Oracle Database software upgrade from a previous release, or because a
patch set is installed, then the script must be run before the database is upgraded.
Therefore, before any new software is installed, you must locate and install the
appropriate utltzuv2.sql patch that is specifically for your combination of old
software version and new time zone file version.
See Also: For the matrix of available patches, visit the Oracle
MetaLink site at http://metalink.oracle.com, and see
Document ID 396906.1.

To run the utltzuv2.sql script, start SQL*Plus, log in as SYSDBA, and run the
following command:
SQL> @?/rdbms/admin/utltzuv2.sql

If your database has data that will be affected by the time zone file update, as
discussed in the preceding section, then back up the timestamp data to an alternative
format before you upgrade the time zone file. After the upgrade, update the data using
the backup that you created, to ensure that the data is stored based on the new rules.
The following example illustrates the update process:
Example 4–5 Upgrading the Time Zone File and Correcting Affected Timestamp Data

Let's assume that the application data contains the following table with a TIMESTAMP
WITH TIME ZONE column.
4-18 Oracle Database Globalization Support Guide

Upgrading the Time Zone File

CREATE TABLE tztab(x NUMBER PRIMARY KEY, y TIMESTAMP WITH TIME ZONE);
INSERT INTO tztab VALUES(1, TIMESTAMP '2007-11-02 12:00:00 America/Los_Angeles');

Before upgrading, create a table tztab_back in order to back up the timestamps from
column y in text format:
CREATE TABLE tztab_back(x NUMBER PRIMARY KEY, y VARCHAR2(256));
INSERT INTO tztab_back SELECT x, TO_CHAR(y, 'YYYY-MM-DD HH24.MI.SSXFF TZR') FROM
tztab;

To reduce the number of rows processed, you can add a WHERE clause and back up
only those timestamps that are affected by the relevant time zone region change. In
this example, the clause could be:
WHERE y > TIMESTAMP '2007-01-01 00:00:00 +00:00'

After upgrading, update the data in the table tztab using the value in tztab_back,
as follows:
UPDATE tztab t SET t.y =
(SELECT to_timestamp_tz(t1.y,'YYYY-MM-DD HH24.MI.SSXFF TZR')
FROM tztab_back t1
WHERE t.x = t1.x);

If you added the WHERE clause when populating tztab_back, then add the same
clause to the UPDATE statement as follows:
UPDATE tztab t SET t.y =
(SELECT to_timestamp_tz(t1.y,'YYYY-MM-DD HH24.MI.SSXFF TZR')
FROM tztab_back t1
WHERE t.x = t1.x)
WHERE t.y > TIMESTAMP '2007-01-01 00:00:00 +00:00'

The Export utility cannot be used to correct the timestamps,
because timestamps are exported in the internal storage format.
Export followed by Import never changes the values.

Note:

Although the transition rule changes may affect data of TIMESTAMP WITH LOCAL
TIME ZONE datatype, there is no way to upgrade the data. The data cannot be
upgraded because this datatype does not preserve the original time zone/region
associated with the data.
Customers who update the time zone file in a database, and who use time zone
regions that are affected by the new file version, are required to update the time zone
file of all database clients. Additionally, all other databases communicating with this
database must be updated to the same version. This ensures that the whole database
environment will have the same version of the time zone file. This is not a requirement
for customers not using the affected regions. However, Oracle recommends that you
do so.
You can find the matrix of available patches for updating your
time zone files by going to Oracle MetaLink at
http://metalink.oracle.com and reading Document ID
396906.1.

Note:

Datetime Datatypes and Time Zone Support 4-19

Upgrading the Time Zone File

See Also: $ORACLE_
HOME/oracore/zoneinfo/timezdif.csv, provided with your
Oracle Database software installation, for a full list of time zones
changed since Oracle9i, and Oracle Database Upgrade Guide for
upgrade information

The utltzuv2.sql script that was provided for Oracle Database 10g to update its
time zone file to version 3 uses an external table based on the supplied
timezdif.csv file to describe time zone changes introduced in the version of the
time zone file associated with the script and in the previous versions. To access this
data yourself, for example, to check the years in which a changed rule is valid, create
an equivalent external table as in the following example. Replace $ORACLE_HOME with
the actual path to the Oracle Home directory of your Oracle Database software
installation.
Example 4–6 Sample External Table to Query Contents of timezdif.csv

The following example creates an external table whose contents come from the file
$ORACLE_HOME/oracore/zoneinfo/timezdif.csv:
CONNECT / AS SYSDBA
CREATE DIRECTORY work_dir AS '$ORACLE_HOME/oracore/zoneinfo/';
GRANT READ ON DIRECTORY work_dir TO SCOTT;
CONNECT scott/tiger
CREATE TABLE TZONEDIFTAB (
VERSION
NUMBER,
TIMEZONE_NAME VARCHAR2(64),
FROM_YEAR
NUMBER,
TO_YEAR
NUMBER
)
ORGANIZATION EXTERNAL
(TYPE oracle_loader
DEFAULT DIRECTORY work_dir
ACCESS PARAMETERS
(
RECORDS DELIMITED BY newline SKIP 3
FIELDS TERMINATED BY "," OPTIONALLY ENCLOSED BY "'"
(
VERSION
CHAR(5),
TIMEZONE_NAME CHAR(64),
FROM_YEAR
CHAR(5),
TO_YEAR
CHAR(5)
)
)
LOCATION ('timezdif.csv')
)
REJECT LIMIT UNLIMITED;
SELECT * FROM TZONEDIFTAB;
VERSION
---------3
3
...

TIMEZONE_NAME
FROM_YEAR
TO_YEAR
---------------------------------------- ---------- ---------Asia/Hong_Kong
1998
null
Asia/Tehran
2024
2027

4-20 Oracle Database Globalization Support Guide

Setting the Session Time Zone

Setting the Database Time Zone
Set the database time zone when the database is created by using the SET TIME_ZONE
clause of the CREATE DATABASE statement. If you do not set the database time zone,
then it defaults to the time zone of the server's operating system.
The time zone may be set to an absolute offset from UTC or to a named region. To set
the time zone to an offset from UTC, use a statement similar to the following example:
CREATE DATABASE db01
...
SET TIME_ZONE='-05:00';

The range of valid offsets is -12:00 to +14:00.
To set the time zone to a named region, use a statement similar to the following
example:
CREATE DATABASE db01
...
SET TIME_ZONE='Europe/London';

Note: The database time zone is relevant only for TIMESTAMP
WITH LOCAL TIME ZONE columns. Oracle recommends that you
set the database time zone to UTC (0:00) to avoid data conversion
and improve performance when data is transferred among
databases. This is especially important for distributed databases,
replication, and exporting and importing.

You can change the database time zone by using the SET TIME_ZONE clause of the
ALTER DATABASE statement. For example:
ALTER DATABASE SET TIME_ZONE='05:00';
ALTER DATABASE SET TIME_ZONE='Europe/London';

The ALTER DATABASE SET TIME_ZONE statement returns an error if the database
contains a table with a TIMESTAMP WITH LOCAL TIME ZONE column and the
column contains data.
The change does not take effect until the database has been shut down and restarted.
You can find out the database time zone by entering the following query:
SELECT dbtimezone FROM DUAL;

Setting the Session Time Zone
You can set the default session time zone with the ORA_SDTZ environment variable.
When users retrieve TIMESTAMP WITH LOCAL TIME ZONE data, Oracle Database
returns it in the users' session time zone. The session time zone also takes effect when
a TIMESTAMP value is converted to the TIMESTAMP WITH TIME ZONE or
TIMESTAMP WITH LOCAL TIME ZONE datatype.

Datetime Datatypes and Time Zone Support 4-21

Converting Time Zones With the AT TIME ZONE Clause

Setting the session time zone does not affect the value
returned by the SYSDATE and SYSTIMESTAMP SQL function.
SYSDATE returns the date and time of the operating system on
which the database resides, taking into account the time zone of the
database server's operating system that was in effect when the
database was started.

Note:

The ORA_SDTZ environment variable can be set to the following values:
■

Operating system local time zone ('OS_TZ')

■

Database time zone ('DB_TZ')

■

Absolute offset from UTC (for example, '-05:00')

■

Time zone region name (for example, 'Europe/London')

To set ORA_SDTZ, use statements similar to one of the following in a UNIX
environment (C shell):
%
%
%
%

setenv
setenv
setenv
setenv

ORA_SDTZ
ORA_SDTZ
ORA_SDTZ
ORA_SDTZ

'OS_TZ'
'DB_TZ'
'-05:00'
'Europe/London'

You can change the time zone for a specific SQL session with the SET TIME_ZONE
clause of the ALTER SESSION statement.
TIME_ZONE can be set to the following values:
■

Default local time zone when the session was started (local)

■

Database time zone (dbtimezone)

■

Absolute offset from UTC (for example, '+10:00')

■

Time zone region name (for example, 'Asia/Hong_Kong')

Use ALTER SESSION statements similar to the following:
ALTER
ALTER
ALTER
ALTER

SESSION
SESSION
SESSION
SESSION

SET
SET
SET
SET

TIME_ZONE=local;
TIME_ZONE=dbtimezone;
TIME_ZONE='+10:00';
TIME_ZONE='Asia/Hong_Kong';

You can find out the current session time zone by entering the following query:
SELECT sessiontimezone FROM DUAL;

Converting Time Zones With the AT TIME ZONE Clause
A datetime SQL expression can be one of the following:
■

A datetime column

■

A compound expression that yields a datetime value

A datetime expression can include an AT LOCAL clause or an AT TIME ZONE clause.
If you include an AT LOCAL clause, then the result is returned in the current session
time zone. If you include the AT TIME ZONE clause, then use one of the following
settings with the clause:

4-22 Oracle Database Globalization Support Guide

Support for Daylight Saving Time

■

Time zone offset: The string '(+|-)HH:MM' specifies a time zone as an offset from
UTC. For example, '-07:00' specifies the time zone that is 7 hours behind UTC.
For example, if the UTC time is 11:00 a.m., then the time in the '-07:00' time
zone is 4:00 a.m.
DBTIMEZONE: Oracle Database uses the database time zone established (explicitly
or by default) during database creation.
SESSIONTIMEZONE: Oracle Database uses the session time zone established by
default or in the most recent ALTER SESSION statement.
Time zone region name: Oracle Database returns the value in the time zone
indicated by the time zone region name. For example, you can specify
Asia/Hong_Kong.
An expression: If an expression returns a character string with a valid time zone
format, then Oracle Database returns the input in that time zone. Otherwise,
Oracle Database returns an error.

The following example converts the datetime value in the America/New_York time
zone to the datetime value in the America/Los_Angeles time zone.
Example 4–7 Converting a Datetime Value to Another Time Zone
SELECT FROM_TZ(CAST(TO_DATE('1999-12-01 11:00:00',
'YYYY-MM-DD HH:MI:SS') AS TIMESTAMP), 'America/New_York')
AT TIME ZONE 'America/Los_Angeles' "West Coast Time"
FROM DUAL;
West Coast Time
---------------------------------------------------------01-DEC-99 08.00.00.000000 AM AMERICA/LOS_ANGELES

See Also:

Oracle Database SQL Reference

Support for Daylight Saving Time
Oracle Database automatically determines whether Daylight Saving Time is in effect
for a specified time zone and returns the corresponding local time. The datetime value
is usually sufficient for Oracle Database to determine whether Daylight Saving Time is
in effect for a specified time zone. The periods when Daylight Saving Time begins or
ends are boundary cases. For example, in the Eastern region of the United States, the
time changes from 01:59:59 a.m. to 3:00:00 a.m. when Daylight Saving Time goes into
effect. The interval between 02:00:00 and 02:59:59 a.m. does not exist. Values in that
interval are invalid. When Daylight Saving Time ends, the time changes from 02:00:00
a.m. to 01:00:01 a.m. The interval between 01:00:01 and 02:00:00 a.m. is repeated.
Values from that interval are ambiguous because they occur twice.
To resolve these boundary cases, Oracle Database uses the TZR and TZD format
elements. TZR represents the time zone region in datetime input strings. Examples are
'Australia/North', 'UTC', and 'Singapore'. TZD represents an abbreviated form of
the time zone region with Daylight Saving Time information. Examples are 'PST' for
US/Pacific standard time and 'PDT' for US/Pacific daylight time. To see a list of valid
values for the TZR and TZD format elements, query the TZNAME and TZABBREV
columns of the V$TIMEZONE_NAMES dynamic performance view.
See Also:

"Time Zone Names" on page A-23 for a list of valid time

zones

Datetime Datatypes and Time Zone Support 4-23

Support for Daylight Saving Time

Examples: The Effect of Daylight Saving Time on Datetime Calculations
The TIMESTAMP datatype does not accept time zone values and does not calculate
Daylight Saving Time.
The TIMESTAMP WITH TIME ZONE and TIMESTAMP WITH LOCAL TIME ZONE
datatypes have the following behavior:
■

■

If a time zone region is associated with the datetime value, then the database
server knows the Daylight Saving Time rules for the region and uses the rules in
calculations.
Daylight Saving Time is not calculated for regions that do not use Daylight Saving
Time.

The rest of this section contains examples that use datetime datatypes. The examples
use the global_orders table. It contains the orderdate1 column of TIMESTAMP
datatype and the orderdate2 column of TIMESTAMP WITH TIME ZONE datatype.
The global_orders table is created as follows:
CREATE TABLE global_orders ( orderdate1 TIMESTAMP(0),
orderdate2 TIMESTAMP(0) WITH TIME ZONE);
INSERT INTO global_orders VALUES ( '28-OCT-00 11:24:54 PM',
'28-OCT-00 11:24:54 PM America/New_York');
Example 4–8 Comparing Daylight Saving Time Calculations Using TIMESTAMP WITH
TIME ZONE and TIMESTAMP
SELECT orderdate1 + INTERVAL '8' HOUR, orderdate2 + INTERVAL '8' HOUR
FROM global_orders;

The following output results:
ORDERDATE1+INTERVAL'8'HOUR
-------------------------29-OCT-00 07.24.54.000000 AM

ORDERDATE2+INTERVAL'8'HOUR
-------------------------29-OCT-00 06.24.54.000000 AM AMERICA/NEW_YORK

This example shows the effect of adding 8 hours to the columns. The time period
includes a Daylight Saving Time boundary (a change from Daylight Saving Time to
standard time). The orderdate1 column is of TIMESTAMP datatype, which does not
use Daylight Saving Time information and thus does not adjust for the change that
took place in the 8-hour interval. The TIMESTAMP WITH TIME ZONE datatype does
adjust for the change, so the orderdate2 column shows the time as one hour earlier
than the time shown in the orderdate1 column.
Note: If you have created a global_orders table for the
previous examples, then drop the global_orders table before
you try Example 4–9 through Example 4–10.
Example 4–9 Comparing Daylight Saving Time Calculations Using TIMESTAMP WITH
LOCAL TIME ZONE and TIMESTAMP

The TIMESTAMP WITH LOCAL TIME ZONE datatype uses the value of TIME_ZONE
that is set for the session environment. The following statements set the value of the
TIME_ZONE session parameter and create a global_orders table. The global_
orders table has one column of TIMESTAMP datatype and one column of TIMESTAMP
WITH LOCAL TIME ZONE datatype.
ALTER SESSION SET TIME_ZONE='America/New_York';
CREATE TABLE global_orders ( orderdate1 TIMESTAMP(0),

4-24 Oracle Database Globalization Support Guide

Support for Daylight Saving Time

orderdate2 TIMESTAMP(0) WITH LOCAL TIME ZONE );
INSERT INTO global_orders VALUES ( '28-OCT-00 11:24:54 PM',
'28-OCT-00 11:24:54 PM' );

Add 8 hours to both columns.
SELECT orderdate1 + INTERVAL '8' HOUR, orderdate2 + INTERVAL '8' HOUR
FROM global_orders;

Because a time zone region is associated with the datetime value for orderdate2, the
Oracle Database server uses the Daylight Saving Time rules for the region. Thus the
output is the same as in Example 4–8. There is a one-hour difference between the two
calculations because Daylight Saving Time is not calculated for the TIMESTAMP
datatype, and the calculation crosses a Daylight Saving Time boundary.
Example 4–10 Daylight Saving Time Is Not Calculated for Regions That Do Not Use
Daylight Saving Time

Set the time zone region to UTC. UTC does not use Daylight Saving Time.
ALTER SESSION SET TIME_ZONE='UTC';

Truncate the global_orders table.
TRUNCATE TABLE global_orders;

Insert values into the global_orders table.
INSERT INTO global_orders VALUES ( '28-OCT-00 11:24:54 PM',
TIMESTAMP '2000-10-28 23:24:54 ' );

Add 8 hours to the columns.
SELECT orderdate1 + INTERVAL '8' HOUR, orderdate2 + INTERVAL '8' HOUR
FROM global_orders;

The following output results.
ORDERDATE1+INTERVAL'8'HOUR
-------------------------29-OCT-00 07.24.54.000000000 AM

ORDERDATE2+INTERVAL'8'HOUR
--------------------------29-OCT-00 07.24.54.000000000 AM UTC

The times are the same because Daylight Saving Time is not calculated for the UTC
time zone region.

Datetime Datatypes and Time Zone Support 4-25

Support for Daylight Saving Time

4-26 Oracle Database Globalization Support Guide

5
Linguistic Sorting and String Searching
This chapter explains linguistic sorting and searching for strings in an Oracle Database
environment.
This chapter contains the following topics:
■

Overview of Oracle Database Sorting Capabilities

■

Using Binary Sorts

■

Using Linguistic Sorts

■

Linguistic Sort Features

■

Case-Insensitive and Accent-Insensitive Linguistic Sorts

■

Performing Linguistic Comparisons

■

Using Linguistic Indexes

■

Searching Linguistic Strings

■

SQL Regular Expressions in a Multilingual Environment

Overview of Oracle Database Sorting Capabilities
Different languages have different sort orders. In addition, different cultures or
countries that use the same alphabets may sort words differently. For example, in
Danish, Æ is after Z, while Y and Ü are considered to be variants of the same letter.
Sort order can be case-sensitive or case-insensitive. Case refers to the condition of
being uppercase or lowercase. For example, in a Latin alphabet, A is the uppercase
glyph for a, the lowercase glyph.
Sort order can ignore or consider diacritics. A diacritic is a mark near or through a
character or combination of characters that indicates a different sound than the sound
of the character without the diacritic. For example, the cedilla (,) in façade is a
diacritic. It changes the sound of c.
Sort order can be phonetic or it can be based on the appearance of the character. For
example, sort order can be based on the number of strokes in East Asian ideographs.
Another common sorting issue is combining letters into a single character. For
example, in traditional Spanish, ch is a distinct character that comes after c, which
means that the correct order is: cerveza, colorado, cheremoya. This means that the
letter c cannot be sorted until Oracle Database has checked whether the next letter is
an h.
Oracle Database provides the following types of sorts:
■

Binary sort
Linguistic Sorting and String Searching

5-1

Using Binary Sorts

■

Monolingual linguistic sort

■

Multilingual linguistic sort

These sorts achieve a linguistically correct order for a single language as well as a sort
based on the multilingual ISO standard (ISO 14651), which is designed to handle many
languages at the same time.

Using Binary Sorts
One way to sort character data is based on the numeric values of the characters
defined by the character encoding scheme. This is called a binary sort. Binary sorts are
the fastest type of sort. They produce reasonable results for the English alphabet
because the ASCII and EBCDIC standards define the letters A to Z in ascending
numeric value.
In the ASCII standard, all uppercase letters appear before
any lowercase letters. In the EBCDIC standard, the opposite is true:
all lowercase letters appear before any uppercase letters.

Note:

When characters used in other languages are present, a binary sort usually does not
produce reasonable results. For example, an ascending ORDER BY query returns the
character strings ABC, ABZ, BCD, ÄBC, when Ä has a higher numeric value than B in the
character encoding scheme. A binary sort is not usually linguistically meaningful for
Asian languages that use ideographic characters.

Using Linguistic Sorts
To produce a sort sequence that matches the alphabetic sequence of characters, another
sort technique must be used that sorts characters independently of their numeric
values in the character encoding scheme. This technique is called a linguistic sort. A
linguistic sort operates by replacing characters with numeric values that reflect each
character's proper linguistic order.
Oracle Database offers two kinds of linguistic sorts: monolingual and multilingual.
This section includes the following topics:
■

Monolingual Linguistic Sorts

■

Multilingual Linguistic Sorts

■

Multilingual Sorting Levels

■

Linguistic Sort Examples

Monolingual Linguistic Sorts
Oracle Database compares character strings in two steps for monolingual sorts. The
first step compares the major value of the entire string from a table of major values.
Usually, letters with the same appearance have the same major value. The second step
compares the minor value from a table of minor values. The major and minor values
are defined by Oracle Database. Oracle Database defines letters with diacritic and case
differences as having the same major value but different minor values.
Each major table entry contains the Unicode code point and major value for a
character. The Unicode code point is a 16-bit binary value that represents a character.

5-2 Oracle Database Globalization Support Guide

Using Linguistic Sorts

Table 5–1 illustrates sample values for sorting a, A, ä, Ä, and b.
Table 5–1

Sample Glyphs and Their Major and Minor Sort Values

Glyph

Major Value

Minor Value

Monolingual linguistic sorting is not available for
non-Unicode multibyte database character sets. If a monolingual
linguistic sort is specified when the database character set is
non-Unicode multibyte, then the default sort order is the binary sort
order of the database character set. One exception is UNICODE_
BINARY. This sort is available for all character sets.

Note:

See Also:

"Overview of Unicode" on page 6-1

Multilingual Linguistic Sorts
Oracle Database provides multilingual linguistic sorts so that you can sort data in
more than one language in one sort. This is useful for regions or languages that have
complex sorting rules and for multilingual databases. As of Oracle Database 11g,
Oracle Database supports all of the sort orders defined by previous releases.
For Asian language data or multilingual data, Oracle Database provides a sorting
mechanism based on the ISO 14651 standard and the Unicode 5.0 standard. Chinese
characters are ordered by the number of strokes, PinYin, or radicals.
In addition, multilingual sorts can handle canonical equivalence and supplementary
characters. Canonical equivalence is a basic equivalence between characters or
sequences of characters. For example, ç is equivalent to the combination of c and ,.
Supplementary characters are user-defined characters or predefined characters in
Unicode that require two code points within a specific code range. You can define up
to 1.1 million code points in one multilingual sort.
For example, Oracle Database supports a monolingual French sort (FRENCH), but you
can specify a multilingual French sort (FRENCH_M). _M represents the ISO 14651
standard for multilingual sorting. The sorting order is based on the GENERIC_M
sorting order and can sort diacritical marks from right to left. Oracle recommends
using a multilingual linguistic sort if the tables contain multilingual data. If the tables
contain only French, then a monolingual French sort may have better performance
because it uses less memory. It uses less memory because fewer characters are defined
in a monolingual French sort than in a multilingual French sort. There is a tradeoff
between the scope and the performance of a sort.
See Also:
■

"Canonical Equivalence" on page 5-7

■

"Supplementary Characters" on page 6-2

Linguistic Sorting and String Searching

5-3

Using Linguistic Sorts

Multilingual Sorting Levels
Oracle Database evaluates multilingual sorts at three levels of precision:
■

Primary Level Sorts

■

Secondary Level Sorts

■

Tertiary Level Sorts

Primary Level Sorts
A primary level sort distinguishes between base letters, such as the difference
between characters a and b. It is up to individual locales to define whether a is before
b, b is before a, or if they are equal. The binary representation of the characters is
completely irrelevant. If a character is an ignorable character, then it is assigned a
primary level order (or weight) of zero, which means it is ignored at the primary level.
Characters that are ignorable on other levels are given an order of zero at those levels.
For example, at the primary level, all variations of bat come before all variations of
bet. The variations of bat can appear in any order, and the variations of bet can
appear in any order:
Bat
bat
BAT
BET
Bet
bet

See Also:

"Ignorable Characters" on page 5-6

Secondary Level Sorts
A secondary level sort distinguishes between base letters (the primary level sort)
before distinguishing between diacritics on a given base letter. For example, the
character Ä differs from the character A only because it has a diacritic. Thus, Ä and A
are the same on the primary level because they have the same base letter (A) but differ
on the secondary level.
The following list has been sorted on the primary level (resume comes before
resumes) and on the secondary level (strings without diacritics come before strings
with diacritics):
resume
résumé
Résumé
Resumes
resumes
résumés

Tertiary Level Sorts
A tertiary level sort distinguishes between base letters (primary level sort), diacritics
(secondary level sort), and case (upper case and lower case). It can also include special
characters such as +, -, and *.
The following are examples of tertiary level sorts:
■

Characters a and A are equal on the primary and secondary levels but different on
the tertiary level because they have different cases.

5-4 Oracle Database Globalization Support Guide

Linguistic Sort Features

■

Characters ä and A are equal on the primary level and different on the secondary
and tertiary levels.
The primary and secondary level orders for the dash character - is 0. That is, it is
ignored on the primary and secondary levels. If a dash is compared with another
character whose primary level order is nonzero, for example, u, then no result for
the primary level is available because u is not compared with anything. In this
case, Oracle Database finds a difference between - and u only at the tertiary level.

The following list has been sorted on the primary level (resume comes before
resumes) and on the secondary level (strings without diacritics come before strings
with diacritics) and on the tertiary level (lower case comes before upper case):
resume
Resume
résumé
Résumé
resumes
Resumes
résumés
Résumés

Linguistic Sort Features
This section contains information about different features that a linguistic sort can
have:
■

Base Letters

■

Ignorable Characters

■

Contracting Characters

■

Expanding Characters

■

Context-Sensitive Characters

■

Canonical Equivalence

■

Reverse Secondary Sorting

■

Character Rearrangement for Thai and Laotian Characters

■

Special Letters

■

Special Combination Letters

■

Special Uppercase Letters

■

Special Lowercase Letters

You can customize linguistic sorts to include the desired characteristics.
See Also:

Chapter 13, "Customizing Locale Data"

Base Letters
Base letters are defined in a base letter table, which maps each letter to its base letter.
For example, a, A, ä, and Ä all map to a, which is the base letter. This concept is
particularly relevant for working with Oracle Text.
See Also:

Oracle Text Reference

Linguistic Sorting and String Searching

5-5

Linguistic Sort Features

Ignorable Characters
Some characters can be ignored in a linguistic sort. These characters are called
ignorable characters. There are two kinds of ignorable characters: diacritics and
punctuation.
Examples of ignorable diacritics are:
■

^, so that rôle is treated the same as role

■

The umlaut, so that naïve is treated the same as naive

An example of an ignorable punctuation character is the dash character -. If it is
ignored, then multi-lingual can be treated that same as multilingual and
e-mail can be treated the same as email.

Contracting Characters
Sorting elements usually consist of a single character, but in some locales, two or more
characters in a character string must be considered as a single sorting element during
sorting. For example, in traditional Spanish, the string ch is composed of two
characters. These characters are called contracting characters in multilingual linguistic
sorting and special combination letters in monolingual linguistic sorting.
Do not confuse a composed character with a contracting character. A composed
character like á can be decomposed into a and ', each with their own encoding. The
difference between a composed character and a contracting character is that a
composed character can be displayed as a single character on a terminal, while a
contracting character is used only for sorting, and its component characters must be
rendered separately.

Expanding Characters
In some locales, certain characters must be sorted as if they were character strings. An
example is the German character ß (sharp s). It is sorted exactly the same as the string
SS. Another example is that ö sorts as if it were oe, after od and before of. These
characters are known as expanding characters in multilingual linguistic sorting and
special letters in monolingual linguistic sorting. Just as with contracting characters,
the replacement string for an expanding character is meaningful only for sorting.

Context-Sensitive Characters
In Japanese, a prolonged sound mark that resembles an em dash — represents a length
mark that lengthens the vowel of the preceding character. The sort order depends on
the vowel that precedes the length mark. This is called context-sensitive sorting. For
example, after the character ka, the — length mark indicates a long a and is treated the
same as a, while after the character ki, the — length mark indicates a long i and is
treated the same as i. Transliterating this to Latin characters, a sort might look like
this:
kaa
ka—
kai
kia
kii
ki—

------

kaa
kai
kia
kii
kii

and ka—
follows
follows
follows
and ki—

are
kakai
kia
are

the same
because i is after a
because i is after a
because i is after a
the same

5-6 Oracle Database Globalization Support Guide

Linguistic Sort Features

Canonical Equivalence
Canonical equivalence is an attribute of a multilingual sort and describes how
equivalent code point sequences are sorted. If canonical equivalence is applied in a
particular linguistic sort, then canonically equivalent strings are treated as equal.
One Unicode code point can be equivalent to a sequence of base letter code points plus
diacritic code points. This is called the Unicode canonical equivalence. For example, ä
equals its base letter a and an umlaut. A linguistic flag, CANONICAL_EQUIVALENCE =
TRUE, indicates that all canonical equivalence rules defined in Unicode need to be
applied in a specific linguistic sort. Oracle Database-defined linguistic sorts include the
appropriate setting for the canonical equivalence flag. You can set the flag to FALSE to
speed up the comparison and ordering functions if all the data is in its composed form.
For example, consider the following strings:
■

äa (a umlaut followed by a)

■

a¨b (a followed by umlaut followed by b)

■

äc (a umlaut followed by c)

If CANONICAL_EQUIVALENCE=FALSE, then the sort order of the strings is:
a¨b
äa
äc

This occurs because a comes before ä if canonical equivalence is not applied.
If CANONICAL_EQUIVALENCE=TRUE, then the sort order of the strings is:
äa
a¨b
äc

This occurs because ä and a¨ are treated as canonically equivalent.
You can use Oracle Locale Builder to view the setting of the canonical equivalence flag
in existing multilingual sorts. When you create a customized multilingual sort with
Oracle Locale Builder, you can set the canonical equivalence flag as desired.
See Also: "Creating a New Linguistic Sort with the Oracle Locale
Builder" on page 13-26 for more information about setting the
canonical equivalence flag

Reverse Secondary Sorting
In French, sorting strings of characters with diacritics first compares base letters from
left to right, but compares characters with diacritics from right to left. For example, by
default, a character with a diacritic is placed after its unmarked variant. Thus Èdit
comes before Edít in a French sort. They are equal on the primary level, and the
secondary order is determined by examining characters with diacritics from right to
left. Individual locales can request that the characters with diacritics be sorted with the
right-to-left rule. Set the REVERSE_SECONDARY linguistic flag to TRUE to enable
reverse secondary sorting.
See Also: "Creating a New Linguistic Sort with the Oracle Locale
Builder" on page 13-26 for more information about setting the
reverse secondary flag

Linguistic Sorting and String Searching

5-7

Linguistic Sort Features

Character Rearrangement for Thai and Laotian Characters
In Thai and Lao, some characters must first change places with the following character
before sorting. Normally, these types of characters are symbols representing vowel
sounds, and the next character is a consonant. Consonants and vowels must change
places before sorting. Set the SWAP_WITH_NEXT linguistic flag for all characters that
must change places before sorting.
See Also: "Creating a New Linguistic Sort with the Oracle Locale
Builder" on page 13-26 for more information about setting the
SWAP_WITH_NEXT flag

Special Letters
Special letters is a term used in monolingual sorts. They are called expanding
characters in multilingual sorts.
See Also:

"Expanding Characters" on page 5-6

Special Combination Letters
Special combination letters is the term used in monolingual sorts. They are called
contracting letters in multilingual sorts.
See Also:

"Contracting Characters" on page 5-6

Special Uppercase Letters
One lowercase letter may map to multiple uppercase letters. For example, in
traditional German, the uppercase letters for ß are SS.
These case conversions are handled by the NLS_UPPER, NLS_LOWER, and NLS_
INITCAP SQL functions, according to the conventions established by the linguistic
sort sequence. The UPPER, LOWER, and INITCAP SQL functions cannot handle these
special characters, because their casing operation is based on binary mapping defined
for the underlying character set, which is not linguistic sensitive.
The NLS_UPPER SQL function returns all uppercase characters from the same
character set as the lowercase string. The following example shows the result of the
NLS_UPPER function when NLS_SORT is set to XGERMAN:
SELECT NLS_UPPER ('große') "Uppercase" FROM DUAL;
Upper
----GROSSE

See Also:

Oracle Database SQL Reference

Special Lowercase Letters
Oracle Database supports special lowercase letters. One uppercase letter may map to
multiple lowercase letters. An example is the Turkish uppercase I becoming a small,
dotless i.

5-8 Oracle Database Globalization Support Guide

Case-Insensitive and Accent-Insensitive Linguistic Sorts

Case-Insensitive and Accent-Insensitive Linguistic Sorts
Operation inside an Oracle database is always sensitive to the case and the accents
(diacritics) of the characters. Sometimes you may need to perform case-insensitive or
accent-insensitive comparisons and sorts.
In previous versions of the database, case-insensitive queries could be achieved by
using the NLS_UPPER and NLS_LOWER SQL functions. The functions change the case
of strings based on a specific linguistic sort definition. This enables you to perform
case-insensitive searches regardless of the language being used. For example, create a
table called test1 as follows:
SQL>
SQL>
SQL>
SQL>
SQL>

CREATE
INSERT
INSERT
INSERT
SELECT

TABLE test1(word VARCHAR2(12));
INTO test1 VALUES('GROSSE');
INTO test1 VALUES('Große');
INTO test1 VALUES('große');
* FROM test1;

WORD
-----------GROSSE
Große
große

Perform a case-sensitive search for GROSSE as follows:
SQL> SELECT word FROM test1 WHERE word='GROSSE';
WORD
-----------GROSSE

Perform a case-insensitive search for GROSSE using the NLS_UPPER function:
SELECT word FROM test1
WHERE NLS_UPPER(word, 'NLS_SORT = XGERMAN') = 'GROSSE';
WORD
-----------GROSSE
Große
große

As of Oracle Database 10g, Oracle Database provides case-insensitive and
accent-insensitive options for linguistic sorts. Oracle Database provides the following
types of monolingual and multilingual linguistic sorts:
■

■

Linguistic sorts that use information about base letters, diacritics, punctuation, and
case. These are the standard monolingual and multilingual linguistic sorts that are
described in "Using Linguistic Sorts" on page 5-2.
Linguistic sorts that use information about base letters, diacritics, and punctuation.
This type of sort is called case-insensitive.
Linguistic sorts that use information about base letters only. This type of sort is
called accent-insensitive. (Accent is another word for diacritic.) An
accent-insensitive sort is always case-insensitive as well.

The rest of this section contains the following topics:
■

Examples of Case-Insensitive and Accent-Insensitive Sorts

■

Specifying a Case-Insensitive or Accent-Insensitive Sort
Linguistic Sorting and String Searching

5-9

Case-Insensitive and Accent-Insensitive Linguistic Sorts

See Also:
■

"NLS_SORT" on page 3-29

■

"NLS_COMP" on page 3-30

Examples of Case-Insensitive and Accent-Insensitive Sorts
The following examples show:
■

A sort that uses information about base letters, diacritics, punctuation, and case

■

A case-insensitive sort

■

An accent-insensitive sort

Example 5–1 Linguistic Sort Using Base Letters, Diacritics, Punctuation, and Case
Information

The following list has been sorted using information about base letters, diacritics,
punctuation, and case:
blackbird
black bird
black-bird
Blackbird
Black-bird
blackbîrd
bläckbird
Example 5–2 Case-Insensitive Linguistic Sort

The following list has been sorted using information about base letters, diacritics, and
punctuation, ignoring case:
black bird
black-bird
Black-bird
blackbird
Blackbird
blackbîrd
bläckbird

black-bird and Black-bird have the same value in the sort, because the only
different between them is case. They could appear interchanged in the list.
Blackbird and blackbird also have the same value in the sort and could appear
interchanged in the list.
Example 5–3 Accent-Insensitive Linguistic Sort

The following list has been sorted using information about base letters only. No
information about diacritics, punctuation, or case has been used.
blackbird
bläckbird
blackbîrd
Blackbird
BlackBird
Black-bird
Black bird

5-10 Oracle Database Globalization Support Guide

Case-Insensitive and Accent-Insensitive Linguistic Sorts

Specifying a Case-Insensitive or Accent-Insensitive Sort
Use the NLS_SORT session parameter to specify a case-insensitive or accent-insensitive
sort:
■
■

Append _CI to an Oracle Database sort name for a case-insensitive sort.
Append _AI to an Oracle Database sort name for an accent-insensitive and
case-insensitive sort.

For example, you can set NLS_SORT to the following types of values:
FRENCH_M_AI
XGERMAN_CI

Binary sorts can also be case-insensitive or accent-insensitive. When you specify
BINARY_CI as a value for NLS_SORT, it designates a sort that is accent-sensitive and
case-insensitive. BINARY_AI designates an accent-insensitive and case-insensitive
binary sort. You may want to use a binary sort if the binary sort order of the character
set is appropriate for the character set you are using.
For example, with the NLS_LANG environment variable set to AMERICAN_
AMERICA.WE8ISO8859P1, create a table called test2 and populate it as follows:
SQL>
SQL>
SQL>
SQL>
SQL>
SQL>

CREATE
INSERT
INSERT
INSERT
INSERT
SELECT

TABLE test2 (letter VARCHAR2(10));
INTO test2 VALUES('ä');
INTO test2 VALUES('a');
INTO test2 VALUES('A');
INTO test2 VALUES('Z');
* FROM test2;

LETTER
----------ä
a
A
Z

The default value of NLS_SORT is BINARY. Use the following statement to do a binary
sort of the characters in table test2:
SELECT * FROM test2 ORDER BY letter;

To change the value of NLS_SORT, enter a statement similar to the following:
ALTER SESSION SET NLS_SORT=BINARY_CI;

The following table shows the sort orders that result from setting NLS_SORT to
BINARY, BINARY_CI, and BINARY_AI.
BINARY

BINARY_CI

BINARY_AI

When NLS_SORT=BINARY, uppercase letters come before lowercase letters. Letters
with diacritics appear last.

Linguistic Sorting and String Searching

5-11

Case-Insensitive and Accent-Insensitive Linguistic Sorts

When the sort considers diacritics but ignores case (BINARY_CI), the letters with
diacritics appear last.
When both case and diacritics are ignored (BINARY_AI), ä is sorted with the other
characters whose base letter is a. All the characters whose base letter is a occur before
z.
You can use binary sorts for better performance when the character set is US7ASCII or
another character set that has the same sort order as the binary sorts.
The following table shows the sort orders that result from German sorts for the table.
GERMAN

GERMAN_CI GERMAN_AI

A German sort places lowercase letters before uppercase letters, and ä occurs before Z.
When the sort ignores both case and diacritics (GERMAN_AI), ä appears with the other
characters whose base letter is a.

Linguistic Sort Examples
The examples in this section demonstrate a binary sort, a monolingual sort, and a
multilingual sort. To prepare for the examples, create and populate a table called
test3. Enter the following statements:
SQL>
SQL>
SQL>
SQL>

CREATE
INSERT
INSERT
INSERT

TABLE test3 (name VARCHAR2(20));
INTO test3 VALUES('Diet');
INTO test3 VALUES('À voir');
INTO test3 VALUES('Freizeit');

Example 5–4 Binary Sort

The ORDER BY clause uses a binary sort.
SQL> SELECT * FROM test3 ORDER BY name;

You should see the following output:
Diet
Freizeit
À voir

Note that a binary sort results in À voir being at the end of the list.
Example 5–5 Monolingual German Sort

Use the NLSSORT function with the NLS_SORT parameter set to german to obtain a
German sort.
SQL> SELECT * FROM test3 ORDER BY NLSSORT(name, 'NLS_SORT=german');

You should see the following output:
À voir
Diet
Freizeit

5-12 Oracle Database Globalization Support Guide

Performing Linguistic Comparisons

Note that À voir is at the beginning of the list in a German sort.
Example 5–6 Comparing a Monolingual German Sort to a Multilingual Sort

Insert the character string shown in Figure 5–1 into test. It is a D with a crossbar
followed by ñ.
Figure 5–1 Character String

Perform a monolingual German sort by using the NLSSORT function with the NLS_
SORT parameter set to german.
SQL> SELECT * FROM test2 ORDER BY NLSSORT(name, 'NLS_SORT=german');

The output from the German sort shows the new character string last in the list of
entries because the characters are not recognized in a German sort.
Perform a multilingual sort by entering the following statement:
SQL> SELECT * FROM test2 ORDER BY NLSSORT(name, 'NLS_SORT=generic_m');

The output shows the new character string after Diet, following ISO sorting rules.
See Also:
■
■

"The NLSSORT Function" on page 9-7
"NLS_SORT" on page 3-29 for more information about setting
and changing the NLS_SORT parameter

Performing Linguistic Comparisons
When performing SQL comparison operations, characters are compared according to
their binary values. A character is greater than another if it has a higher binary value.
Because the binary sequences rarely match the linguistic sequences for most
languages, such comparisons may not be meaningful for a typical user. To achieve a
meaningful comparison, you can specify behavior by using the session parameters
NLS_COMP and NLS_SORT. The way you set these two parameters determines the
rules by which characters are sorted and compared.
The NLS_COMP setting determines how NLS_SORT is handled by the SQL operations.
There are three valid values for NLS_COMP:
■

BINARY
All SQL sorts and comparisons are based on the binary values of the string
characters, regardless of the value set to NLS_SORT. This is the default setting.

■

LINGUISTIC
All SQL sorting and comparison are based on the linguistic rule specified by NLS_
SORT. For example, NLS_COMP=LINGUISTIC and NLS_SORT=BINARY_CI means
the collation sensitive SQL operations will use binary value for sorting and
comparison but ignore character case.

■

ANSI

Linguistic Sorting and String Searching

5-13

Performing Linguistic Comparisons

A limited set of SQL functions honor the NLS_SORT setting. ANSI is available for
backward compatibility only. In general, you should set NLS_COMP to
LINGUISTIC when performing linguistic comparison.
Table 5–2 shows how different SQL operations behave with these different settings.
Table 5–2

Linguistic Comparison Behavior with NLS_COMP Settings
BINARY

LINGUISTIC

ANSI

Binary

Honors NLS_SORT

Binary

DECODE

Binary

Honors NLS_SORT

Binary

INSTRx

Binary

Honors NLS_SORT

Binary

LEAST, GREATEST

Binary

Honors NLS_SORT

Binary

MAX, MIN

Binary

Honors NLS_SORT

Binary

NLS_INITCAP

Honors NLS_SORT

NLS_LOWER

Honors NLS_SORT

NLS_UPPER

Honors NLS_SORT

NLSSORT

Honors NLS_SORT

NULLIF

Binary

Honors NLS_SORT

Binary

REGEXP_COUNT

Honors NLS_SORT

REGEXP_INSTR

Honors NLS_SORT

REGEXP_LIKE

Honors NLS_SORT

REGEXP_REPLACE

Honors NLS_SORT

REGEXP_SUBSTR

Honors NLS_SORT

REPLACE

Binary

Honors NLS_SORT

Binary

RTRIM, TRIM, LTRIM

Binary

Honors NLS_SORT

Binary

TRANSLATE, TRANSLATE USING

Binary

Honors NLS_SORT

Binary

=, !=, >, <, >=, <=

Binary

Honors NLS_SORT

BETWEEN, NOT BETWEEN

Binary

Honors NLS_SORT

CASE

Binary

Honors NLS_SORT

Binary

DISTINCT

Binary

Honors NLS_SORT

Binary

GROUP

Binary

Honors NLS_SORT

Binary

GROUP BY

Binary

Honors NLS_SORT

Binary

HAVING

Binary

Honors NLS_SORT

IN, NOT IN

Binary

Honors NLS_SORT

Binary

Honors NLS_SORT

Binary

ORDER BY

Honors NLS_SORT

START WITH

Binary

Honors NLS_SORT

UNIQUE

Binary

Honors NLS_SORT

Binary

SQL Operators
UNION, INTERSECT, MINUS
SQL Functions

SQL Expressions

5-14 Oracle Database Globalization Support Guide

Performing Linguistic Comparisons

See "NLS_COMP" and "NLS_SORT" for information regarding these parameters.

Linguistic Comparison Examples
The following examples illustrate behavior with different NLS_COMP settings.
Example 5–7 Binary Comparison Binary Sort

The following illustrates behavior with a binary setting:
SQL> ALTER SESSION SET NLS_COMP=BINARY;
SQL> ALTER SESSION SET NLS_SORT=BINARY;
SQL> SELECT ename FROM emp1;
ENAME
---------------------Mc Calla
MCAfee
McCoye
Mccathye
McCafeé
5 rows selected
SQL> SELECT ename FROM emp1 WHERE ename LIKE 'McC%e';
ENAME
---------------------McCoye
1 row selected
Example 5–8 Linguistic Comparison Binary Case-Insensitive Sort

The following illustrates behavior with a case-insensitive setting:
SQL> ALTER SESSION SET NLS_COMP=LINGUISTIC;
SQL> ALTER SESSION SET NLS_SORT=BINARY_CI;
SQL> SELECT ename FROM emp1 WHERE ename LIKE 'McC%e';
ENAME
---------------------McCoye
Mccathye
2 rows selected
Example 5–9 Linguistic Comparison Binary Accent-Insensitive Sort

The following illustrates behavior with an accent-insensitive setting:
SQL> ALTER SESSION SET NLS_COMP=LINGUISTIC;
SQL> ALTER SESSION SET NLS_SORT=BINARY_AI;
SQL> SELECT ename FROM emp1 WHERE ename LIKE 'McC%e';
ENAME
---------------------McCoye
Mccathye
McCafeé

Linguistic Sorting and String Searching

5-15

Performing Linguistic Comparisons

3 rows selected
Example 5–10

Linguistic Comparisons Returning Fewer Rows

Some operations may return fewer rows after applying linguistic rules. For example,
with a binary setting, McAfee and Mcafee are different:
SQL> ALTER SESSION SET NLS_COMP=BINARY;
SQL> ALTER SESSION SET NLS_SORT=BINARY;
SQL> SELECT DISTINCT ename FROM emp2;
ENAME
---------------------McAfee
Mcafee
McCoy
3 rows selected

However, with a case-insensitive setting, McAfee and Mcafee are the same:
SQL> ALTER SESSION SET NLS_COMP=LINGUISTIC;
SQL> ALTER SESSION SET NLS_SORT=BINARY_CI;
SQL> SELECT DISTINCT ename FROM emp2;
ENAME
---------------------McAfee
McCoy
2 rows selected

In this example, either McAfee or Mcafee could be returned from the DISTINCT
operation. There is no guarantee exactly which one will be picked.
Example 5–11

Linguistic Comparisons Using XSPANISH

There are cases where characters the are same using binary comparison but different
using linguistic comparison. For example, with a binary setting, the character C in
Cindy, Chad, and Clara represents the same letter C:
SQL> ALTER SESSION SET NLS_COMP=BINARY;
SQL> ALTER SESSION SET NLS_SORT=BINARY;
SQL> SELECT ename FROM emp3 WHERE ename LIKE 'C%';
ENAME
---------------------Cindy
Chad
Clara
3 rows selected

In a database session with the linguistic rule set to traditional Spanish, XSPANISH, ch
is treated as one character. So the letter c in Chad is different than the letter C in Cindy
and Clara:
SQL> ALTER SESSION SET NLS_COMP=LINGUISTIC;
SQL> ALTER SESSION SET NLS_SORT=XSPANISH;
SQL> SELECT ename FROM emp3 WHERE ename LIKE 'C%';

5-16 Oracle Database Globalization Support Guide

Using Linguistic Indexes

ENAME
---------------------Cindy
Clara
2 rows selected

And the letter c in combination ch is different than the c standing by itself:
SQL> SELECT REPLACE ('character', 'c', 't') "Changes" FROM DUAL;
Changes
--------------------charatter

Using Linguistic Indexes
Linguistic sorting is language-specific and requires more data processing than binary
sorting. Using a binary sort for ASCII is accurate and fast because the binary codes for
ASCII characters reflect their linguistic order. When data in multiple languages is
stored in the database, you may want applications to sort the data returned from a
SELECT...ORDER BY statement according to different sort sequences depending on
the language. You can accomplish this without sacrificing performance by using
linguistic indexes. Although a linguistic index for a column slows down inserts and
updates, it greatly improves the performance of linguistic sorting with the ORDER BY
clause and the WHERE clause.
You can create a function-based index that uses languages other than English. The
index does not change the linguistic sort order determined by NLS_SORT. The
linquistic index simply improves the performance.
The following statement creates an index based on a German sort:
CREATE TABLE my_table(name VARCHAR(20) NOT NULL);
CREATE INDEX nls_index ON my_table (NLSSORT(name, 'NLS_SORT = German'));
/*The NOT NULL in the CREATE TABLE statement ensures that the index is used*/

After the index has been created, enter a SELECT statement similar to the following
example:
SELECT * FROM my_table ORDER BY name
WHERE name LIKE ’Hein%’;

It returns the result much faster than the same SELECT statement without a linguistic
index.
The rest of this section contains the following topics:
■

Supported SQL Operations and Functions for Linguistic Indexes
Linguistic Indexes for Multiple Languages

■

Requirements for Using Linguistic Indexes
See Also:
■
■

Oracle Database Concepts
Oracle Database SQL Reference for more information about
function-based indexes

Linguistic Sorting and String Searching

5-17

Using Linguistic Indexes

Supported SQL Operations and Functions for Linguistic Indexes
Linguistic index support is available for the following collation-sensitive SQL
operations and SQL functions:
■

Comparison conditions =, !=, >, <, >=, <=

■

Range conditions BETWEEN | NOT BETWEEN

■

IN | NOT IN

■

ORDER BY

■

GROUP BY

■

LIKE (LIKE, LIKE2, LIKE4, LIKEC)

■

DISTINCT

■

UNIQUE

■

UNION

■

INTERSECT

■

MINUS

The SQL functions in the following list cannot utilize linguistic index:
■

INSTR (INSTR, INSTRB, INSTR2, INSTR4, INSTRC)

■

MAX

■

MIN

■

REPLACE

■

TRIM

■

LTRIM

■

RTRIM

■

TRANSLATE

Linguistic Indexes for Multiple Languages
There are three ways to build linguistic indexes for data in multiple languages:
■

Build a linguistic index for each language that the application supports. This
approach offers simplicity but requires more disk space. For each index, the rows
in the language other than the one on which the index is built are collated together
at the end of the sequence. The following example builds linguistic indexes for
French and German.
CREATE INDEX french_index ON employees (NLSSORT(employee_id, 'NLS_
SORT=FRENCH'));
CREATE INDEX german_index ON employees (NLSSORT(employee_id, 'NLS_
SORT=GERMAN'));

Oracle Database chooses the index based on the NLS_SORT session parameter or
the arguments of the NLSSORT function specified in the ORDER BY clause. For
example, if the NLS_SORT session parameter is set to FRENCH, then Oracle
Database uses french_index. When it is set to GERMAN, Oracle Database uses
german_index.
■

Build a single linguistic index for all languages. This requires a language column
(LANG_COL in "Example: Setting Up a French Linguistic Index" on page 5-19) to be

5-18 Oracle Database Globalization Support Guide

Using Linguistic Indexes

used as a parameter of the NLSSORT function. The language column contains
NLS_LANGUAGE values for the data in the column on which the index is built. The
following example builds a single linguistic index for multiple languages. With
this index, the rows with the same values for NLS_LANGUAGE are sorted together.
CREATE INDEX i ON t (NLSSORT(col, 'NLS_SORT=' || LANG_COL));

Queries choose an index based on the argument of the NLSSORT function specified
in the ORDER BY clause.
■

Build a single linguistic index for all languages using one of the multilingual
linguistic sorts such as GENERIC_M or FRENCH_M. These indexes sort characters
according to the rules defined in ISO 14651. For example:
CREATE INDEX i on t (NLSSORT(col,
'NLS_SORT=GENERIC_M');

See Also: "Multilingual Linguistic Sorts" on page 5-3 for more
information about Unicode sorts

Requirements for Using Linguistic Indexes
The following are requirements for using linguistic indexes:
■
■

Set NLS_SORT Appropriately
Specify NOT NULL in a WHERE Clause If the Column Was Not Declared NOT
NULL

This section also includes:
■

Example: Setting Up a French Linguistic Index

Set NLS_SORT Appropriately
The NLS_SORT parameter should indicate the linguistic definition you want to use for
the linguistic sort. If you want a French linguistic sort order, then NLS_SORT should be
set to FRENCH. If you want a German linguistic sort order, then NLS_SORT should be
set to GERMAN.
There are several ways to set NLS_SORT. You should set NLS_SORT as a client
environment variable so that you can use the same SQL statements for all languages.
Different linguistic indexes can be used when NLS_SORT is set in the client
environment.
See Also:

"NLS_SORT" on page 3-29

Specify NOT NULL in a WHERE Clause If the Column Was Not Declared NOT NULL
When you want to use the ORDER BY column_name clause with a column that has a
linguistic index, include a WHERE clause like the following example:
WHERE NLSSORT(column_name) IS NOT NULL

This WHERE clause is not necessary if the column has already been defined as a NOT
NULL column in the schema.

Example: Setting Up a French Linguistic Index
The following example shows how to set up a French linguistic index. You may want
to set NLS_SORT as a client environment variable instead of using the ALTER SESSION
statement.

Linguistic Sorting and String Searching

5-19

Searching Linguistic Strings

ALTER SESSION SET NLS_SORT='FRENCH';
CREATE INDEX test_idx ON test4(NLSSORT(name, 'NLS_SORT=FRENCH'));
SELECT * FROM test4 ORDER BY col;
ALTER SESSION SET NLS_COMP=LINGUISTIC;
SELECT * FROM test4 WHERE name > 'Henri';

The SQL functions MAX( ) and MIN( ) cannot use linguistic
indexes when NLS_COMP is set to LINGUISTIC.

Note:

Searching Linguistic Strings
Searching and sorting are related tasks. Organizing data and processing it in a
linguistically meaningful order is necessary for proper business processing. Searching
and matching data in a linguistically meaningful way depends on what sort order is
applied. For example, searching for all strings greater than c and less than f produces
different results depending on the value of NLS_SORT. In an ASCII binary sort the
search finds any strings that start with d or e but excludes entries that begin with
upper case D or E or accented e with a diacritic, such as ê. Applying an
accent-insensitive binary sort returns all strings that start with d, D, and accented e,
such as Ê or ê. Applying the same search with NLS_SORT set to XSPANISH also
returns strings that start with ch, because ch is treated as a composite character that
sorts between c and d in traditional Spanish. This chapter discusses the kinds of sorts
that Oracle Database offers and how they affect string searches by SQL and SQL
regular expressions.
See Also:
■
■

"Linguistic Sort Features" on page 5-5
"SQL Regular Expressions in a Multilingual Environment" on
page 5-20

SQL Regular Expressions in a Multilingual Environment
Regular expressions provide a powerful method of identifying patterns of strings
within a body of text. Usage ranges from a simple search for a string such as San
Francisco to the more complex task of extracting all URLs to finding all words
whose every second character is a vowel. SQL and PL/SQL support regular
expressions in Oracle Database 10g.
Traditional regular expression engines were designed to address only English text.
However, regular expression implementations can encompass a wide variety of
languages with characteristics that are very different from western European text. The
implementation of regular expressions in Oracle Database is based on the Unicode
Regular Expression Guidelines. The REGEXP SQL functions work with all character
sets that are supported as database character sets and national character sets.
Moreover, Oracle Database enhances the matching capabilities of the POSIX regular
expression constructs to handle the unique linguistic requirements of matching
multilingual data.
Oracle Database enhancements of the linguistic-sensitive operators are described in
the following sections:
■

Character Range '[x-y]' in Regular Expressions

■

Collation Element Delimiter '[. .]' in Regular Expressions

■

Character Class '[: :]' in Regular Expressions

5-20 Oracle Database Globalization Support Guide

SQL Regular Expressions in a Multilingual Environment

■

Equivalence Class '[= =]' in Regular Expressions

■

Examples: Regular Expressions
See Also:
■

■

Oracle Database Application Developer's Guide - Fundamentals for
more information about regular expression syntax
Oracle Database SQL Reference for more information about
REGEX SQL functions

Character Range '[x-y]' in Regular Expressions
According to the POSIX standard, a range in a regular expression includes all collation
elements between the start point and the end point of the range in the linguistic
definition of the current locale. Therefore, ranges in regular expressions are meant to
be linguistic ranges, not byte value ranges, because byte value ranges depend on the
platform, and the end user should not be expected to know the ordering of the byte
values of the characters. The semantics of the range expression must be independent of
the character set. This implies that a range such as [a-d] includes all the letters
between a and d plus all of those letters with diacritics, plus any special case collation
element such as ch in Traditional Spanish that is sorted as one character.
Oracle Database interprets range expressions as specified by the NLS_SORT parameter
to determine the collation elements covered by a given range. For example:
Expression:
NLS_SORT:
Does not match:
NLS_SORT:
Matches:

[a-d]e
BINARY
cheremoya
XSPANISH
>>che<>Catalog<<
>>catalogue<<
>>CATALOG<<

Oracle Database SQL syntax:
SQL> ALTER SESSION SET NLS_SORT='GENERIC_M_CI';
SQL> SELECT col FROM test WHERE REGEXP_LIKE(col,'catalog(ue)?');
Example 5–13

Case Insensitivity Overridden by the Runtime Match Option

Expression: catalog(ue)?
NLS_SORT: GENERIC_M_CI
Match option: 'c'
Matches:
>>catalogue<<
Does not match:
Catalog
CATALOG

Oracle Database SQL syntax:
SQL> ALTER SESSION SET NLS_SORT='GENERIC_M_CI';
SQL> SELECT col FROM test WHERE REGEXP_LIKE(col,'catalog(ue)?','c');
Example 5–14

Matching with the Collation Element Operator [..]

Expression: [^-a-[.ch.]]+
Matches:
>>driver<<
Does not match:

/*with NLS_SORT set to xspanish*/

5-22 Oracle Database Globalization Support Guide

SQL Regular Expressions in a Multilingual Environment

cab

Oracle Database SQL syntax:
SQL> SELECT col FROM test WHERE REGEXP_LIKE(col,'[^-a-[.ch.]]+');
Example 5–15

Matching with the Character Class Operator [::]

This expression looks for 6-character strings with lowercase characters. Note that
accented characters are matched as lowercase characters.
Expression: [[:lower:]]{6}
Database character set: WE8ISO8859P1
Matches:
>>maître<<
>>mòbile<<
>>pájaro<<
>>zurück<<

Oracle Database SQL syntax:
SQL> SELECT col FROM test WHERE REGEXP_LIKE(col,'[[:lower:]]{6}');
Example 5–16

Matching with the Base Letter Operator [==]

Expression: r[[=e=]]sum[[=e=]]
Matches:
>>resume<<
>>résumé<<
>>résume<<
>>resumé<<

Oracle Database SQL syntax:
SQL> SELECT col FROM test WHERE REGEXP_LIKE(col,'r[[=e=]]sum[[=e=]]');

See Also:
■

■

Oracle Database Application Developer's Guide - Fundamentals for
more information about regular expression syntax
Oracle Database SQL Reference for more information about
REGEX SQL functions

Linguistic Sorting and String Searching

5-23

SQL Regular Expressions in a Multilingual Environment

5-24 Oracle Database Globalization Support Guide

6
Supporting Multilingual Databases with
Unicode
This chapter illustrates how to use Unicode in an Oracle Database environment. This
chapter includes the following topics:
■

Overview of Unicode

■

What is Unicode?

■

Implementing a Unicode Solution in the Database

■

Unicode Case Studies

■

Designing Database Schemas to Support Multiple Languages

Overview of Unicode
Unicode is a character encoding system that defines every character in most of the
spoken languages in the world.
To overcome the limitations of existing character encodings, several organizations
began working on the creation of a global character set in the late 1980s. The need for
this became even greater with the development of the World Wide Web in the
mid-1990s. The Internet has changed how companies do business, with an emphasis
on the global market that has made a universal character set a major requirement.
A global character set needs to fulfill the following conditions:
■

Contain all major living scripts

■

Support legacy data and implementations

■

Be simple enough that a single implementation of an application is sufficient for
worldwide use

A global character set should also have the following capabilities:
■

Support multilingual users and organizations

■

Conform to international standards

■

Enable worldwide interchange of data

Unicode, which is now in wide use, meets all of the requirments and capabilities of a
global character set.

Supporting Multilingual Databases with Unicode

6-1

What is Unicode?

What is Unicode?
Unicode is a universally encoded character set that enables information from any
language to be stored using a single character set. Unicode provides a unique code
value for every character, regardless of the platform, program, or language.
The Unicode standard has been adopted by many software and hardware vendors.
Many operating systems and browsers now support Unicode. Unicode is required by
standards such as XML, Java, JavaScript, LDAP, and WML. It is also synchronized
with the ISO/IEC 10646 standard.
Oracle Database introduced Unicode as a database character set in Oracle Database 7.
In Oracle Database 11g, Unicode support has been expanded. Oracle Database 11g
release 1 supports Unicode 5.0.
See Also: http://www.unicode.org for more information
about the Unicode standard

This section contains the following topics:
■

Supplementary Characters

■

Unicode Encodings

■

Support for Unicode in Oracle Database

Supplementary Characters
The first version of Unicode was a 16-bit, fixed-width encoding that used two bytes to
encode each character. This enabled 65,536 characters to be represented. However,
more characters need to be supported, especially additional CJK ideographs that are
important for the Chinese, Japanese, and Korean markets.
Unicode defines supplementary characters to meet this need. It uses two 16-bit code
points (also known as supplementary characters) to represent a single character. The
implementation of supplementary characters enables more than a million additional
characters to be defined.
Adding supplementary characters has increased the complexity of Unicode; however,
this is less complex than managing several different encodings in the same
configuration.

Unicode Encodings
The Unicode standard encodes characters in different ways: UTF-8, UCS-2, and
UTF-16. Conversion between different Unicode encodings is a simple bit-wise
operation that is defined in the Unicode standard.
This section contains the following topics:
■

UTF-8 Encoding

■

UCS-2 Encoding

■

UTF-16 Encoding

■

Examples: UTF-16, UTF-8, and UCS-2 Encoding

UTF-8 Encoding
UTF-8 is the 8-bit encoding of Unicode. It is a variable-width encoding and a strict
superset of ASCII. This means that each and every character in the ASCII character set

6-2 Oracle Database Globalization Support Guide

What is Unicode?

is available in UTF-8 with the same code point values. One Unicode character can be 1
byte, 2 bytes, 3 bytes, or 4 bytes in UTF-8 encoding. Characters from the European
scripts are represented in either 1 or 2 bytes. Characters from most Asian scripts are
represented in 3 bytes. Supplementary characters are represented in 4 bytes.
UTF-8 is the Unicode encoding used for HTML and most Internet browsers.
The benefits of UTF-8 are as follows:
■

■

Compact storage requirement for European scripts because it is a strict superset of
ASCII
Ease of migration between ASCII-based characters sets and UTF-8
See Also:
■
■

"Supplementary Characters" on page 6-2
Table B–2, " Unicode Character Code Ranges for UTF-8
Character Codes" on page B-2

UCS-2 Encoding
UCS-2 is a fixed-width, 16-bit encoding. Each character is 2 bytes. UCS-2 is the
Unicode encoding used by Java and Microsoft Windows . UCS-2 supports characters
defined for Unicode 3.0, so there is no support for supplementary characters.
The benefits of UCS-2 over UTF-8 are as follows:
■

More compact storage for Asian scripts, because all characters are two bytes

■

Faster string processing, because characters are fixed-width

■

Better compatibility with Java and Microsoft clients
See Also:

"Supplementary Characters" on page 6-2

UTF-16 Encoding
UTF-16 encoding is the 16-bit encoding of Unicode. UTF-16 is an extension of UCS-2
because it supports the supplementary characters by using two UCS-2 code points for
each supplementary character. UTF-16 is a strict superset of UCS-2.
One character can be either 2 bytes or 4 bytes in UTF-16. Characters from European
and most Asian scripts are represented in 2 bytes. Supplementary characters are
represented in 4 bytes. UTF-16 is the main Unicode encoding used by Microsoft
Windows 2000.
The benefits of UTF-16 over UTF-8 are as follows:
■

■

More compact storage for Asian scripts because most of the commonly used Asian
characters are represented in two bytes.
Better compatibility with Java and Microsoft clients
See Also:
■
■

"Supplementary Characters" on page 6-2
Table B–1, " Unicode Character Code Ranges for UTF-16
Character Codes" on page B-1

Supporting Multilingual Databases with Unicode

6-3

What is Unicode?

Examples: UTF-16, UTF-8, and UCS-2 Encoding
Figure 6–1 shows some characters and their character codes in UTF-16, UTF-8, and
UCS-2 encoding. The last character is a treble clef (a music symbol), a supplementary
character.
Figure 6–1 UTF-16, UTF-8, and UCS-2 Encoding Examples

Character

UTF-16

UTF-8

UCS-2

A
c
Ö

0041
0063
00F6
4E9C
D834 DD1E

41
63
C3 B6
E4 BA 9C
F0 9D 84 9E

0041
0063
00F6
4E9C
N/A

Support for Unicode in Oracle Database
Oracle Database began supporting Unicode as a database character set in release 7.
Table 6–1 summarizes the Unicode character sets supported by Oracle Database.
Table 6–1

Unicode Character Sets Supported by Oracle Database

Character Set

Supported in
RDBMS
Release

Unicode
Encoding

Unicode Version

Database
Character Set

National
Character Set

AL24UTFFSS

7.2 - 8i

UTF-8

1.1

Yes

UTF8

8.0 - 11g

UTF-8

For Oracle Database
release 8.0 through
Oracle8i release 8.1.6: 2.1

Yes

Yes (Oracle9i
Database and
Oracle Database
10g only)

For Oracle8i Database
release 8.1.7 and later: 3.0

6-4 Oracle Database Globalization Support Guide

Implementing a Unicode Solution in the Database

Table 6–1 (Cont.) Unicode Character Sets Supported by Oracle Database

Character Set

Supported in
RDBMS
Release

Unicode
Encoding

UTFE

8.0 - 11g

UTF-EBCDIC

Database
Character Set

National
Character Set

Yes

Oracle9i Database Release Yes
1: 3.0

Unicode Version
For Oracle8i Database
releases 8.0 through 8.1.6:
2.1
For Oracle8i Database
release 8.1.7 and later: 3.0

AL32UTF8

9i - 11g

UTF-8

Oracle9i Database Release
2: 3.1
Oracle Database 10g,
Release 1: 3.2
Oracle Database 10g,
Release2: 4.0
Oracle Database 11g,
Release 1: 5.0
AL16UTF16

9i - 11g

UTF-16

Oracle9i Database Release No
1: 3.0

Yes

Oracle9i Database Release
2: 3.1
Oracle Database 10g,
Release 1: 3.2
Oracle Database 10g,
Release 2: 4.0
Oracle Database 11g,
Release 1: 5.0

Implementing a Unicode Solution in the Database
Unicode characters can be stored in an Oracle database in two ways:
■

■

You can create a Unicode database that enables you to store UTF-8 encoded
characters as SQL CHAR datatypes (CHAR, VARCHAR2, CLOB, and LONG).
If you prefer to implement Unicode support incrementally, or if you need to
support multilingual data only in certain columns, then you can store Unicode
data in either the UTF-16 or UTF-8 encoding form in SQL NCHAR datatypes
(NCHAR, NVARCHAR2, and NCLOB). The SQL NCHAR datatypes are called Unicode
datatypes because they are used only for storing Unicode data.
You can combine a Unicode database solution with a
Unicode datatype solution.

Note:

The following sections explain how to use the two Unicode solutions and how to
choose between them:
■

Enabling Multilingual Support with Unicode Databases

■

Enabling Multilingual Support with Unicode Datatypes

■

How to Choose Between a Unicode Database and a Unicode Datatype Solution

Supporting Multilingual Databases with Unicode

6-5

Implementing a Unicode Solution in the Database

■

Comparing Unicode Character Sets for Database and Datatype Solutions

Enabling Multilingual Support with Unicode Databases
The database character set specifies the encoding to be used in the SQL CHAR
datatypes as well as the metadata such as table names, column names, and SQL
statements. A Unicode database is a database with a UTF-8 character set as the
database character set. There are three Oracle character sets that implement the UTF-8
encoding. The first two are designed for ASCII-based platforms while the third one
should be used on EBCDIC platforms.
■

AL32UTF8
The AL32UTF8 character set supports the latest version of the Unicode standard. It
encodes characters in one, two, or three bytes. Supplementary characters require
four bytes. It is for ASCII-based platforms.

■

UTF8
The UTF8 character set encodes characters in one, two, or three bytes. It is for
ASCII-based platforms.
Supplementary characters inserted into a UTF8 database do not corrupt the data in
the database. A supplementary character is treated as two separate, user-defined
characters that occupy 6 bytes. Oracle recommends that you switch to AL32UTF8
for full support of supplementary characters in the database character set.

■

UTFE
The UTFE character set is for EBCDIC platforms. It is similar to UTF8 on ASCII
platforms, but it encodes characters in one, two, three, and four bytes.
Supplementary characters are converted as two 4-byte characters.

Example 6–1 Creating a Database with a Unicode Character Set

To create a database with the AL32UTF8 character set, use the CREATE DATABASE
statement and include the CHARACTER SET AL32UTF8 clause. For example:
CREATE DATABASE sample
CONTROLFILE REUSE
LOGFILE
GROUP 1 ('diskx:log1.log', 'disky:log1.log') SIZE 50K,
GROUP 2 ('diskx:log2.log', 'disky:log2.log') SIZE 50K
MAXLOGFILES 5
MAXLOGHISTORY 100
MAXDATAFILES 10
MAXINSTANCES 2
ARCHIVELOG
CHARACTER SET AL32UTF8
NATIONAL CHARACTER SET AL16UTF16
DATAFILE
'disk1:df1.dbf' AUTOEXTEND ON,
'disk2:df2.dbf' AUTOEXTEND ON NEXT 10M MAXSIZE UNLIMITED
DEFAULT TEMPORARY TABLESPACE temp_ts
UNDO TABLESPACE undo_ts
SET TIME_ZONE = '+02:00';

Specify the database character set when you create the
database.

Note:

6-6 Oracle Database Globalization Support Guide

Implementing a Unicode Solution in the Database

Enabling Multilingual Support with Unicode Datatypes
An alternative to storing Unicode data in the database is to use the SQL NCHAR
datatypes (NCHAR, NVARCHAR, NCLOB). You can store Unicode characters in columns
of these datatypes regardless of how the database character set has been defined. The
NCHAR datatype is exclusively a Unicode datatype, which means that it stores data
encoded as Unicode.
You can create a table using the NVARCHAR2 and NCHAR datatypes. The column length
specified for the NCHAR and NVARCHAR2 columns always equals the number of
characters instead of the number of bytes:
CREATE TABLE product_information
( product_id
NUMBER(6)
, product_name
NVARCHAR2(100)
, product_description VARCHAR2(1000));

The encoding used in the SQL NCHAR datatypes is the national character set specified
for the database. You can specify one of the following Oracle character sets as the
national character set:
■

AL16UTF16
This is the default character set for SQL NCHAR datatypes. This character set
encodes Unicode data in the UTF-16 encoding. It supports supplementary
characters, which are stored as four bytes.

■

UTF8
When UTF8 is specified for SQL NCHAR datatypes, the data stored in the SQL
datatypes is in UTF-8 encoding.

You can specify the national character set for the SQL NCHAR datatypes when you
create a database using the CREATE DATABASE statement with the NATIONAL
CHARACTER SET clause. The following statement creates a database with
WE8ISO8859P1 as the database character set and AL16UTF16 as the national character
set.
Example 6–2 Creating a Database with a National Character Set
CREATE DATABASE sample
CONTROLFILE REUSE
LOGFILE
GROUP 1 ('diskx:log1.log', 'disky:log1.log') SIZE 50K,
GROUP 2 ('diskx:log2.log', 'disky:log2.log') SIZE 50K
MAXLOGFILES 5
MAXLOGHISTORY 100
MAXDATAFILES 10
MAXINSTANCES 2
ARCHIVELOG
CHARACTER SET WE8ISO8859P1
NATIONAL CHARACTER SET AL16UTF16
DATAFILE
'disk1:df1.dbf' AUTOEXTEND ON,
'disk2:df2.dbf' AUTOEXTEND ON NEXT 10M MAXSIZE UNLIMITED
DEFAULT TEMPORARY TABLESPACE temp_ts
UNDO TABLESPACE undo_ts
SET TIME_ZONE = '+02:00';

Supporting Multilingual Databases with Unicode

6-7

Implementing a Unicode Solution in the Database

How to Choose Between a Unicode Database and a Unicode Datatype Solution
To choose the correct Unicode solution for your database, consider the following
questions:
■

■

Programming environment: What are the main programming languages used in
your applications? How do they support Unicode?
Ease of migration: How easily can your data and applications be migrated to take
advantage of the Unicode solution?
Types of data: Is your data mostly Asian or European? Do you need to store
multilingual documents into LOB columns?
Types of applications: What type of applications are you implementing: a
packaged application or a customized end-user application?

This section describes some general guidelines for choosing a Unicode database or a
Unicode datatype solution. The final decision largely depends on your exact
environment and requirements. This section contains the following topics:
■

When Should You Use a Unicode Database?

■

When Should You Use Unicode Datatypes?

When Should You Use a Unicode Database?
Use a Unicode database in the situations described in Table 6–2.
Table 6–2

Using a Unicode Database

Situation

Explanation

You need easy code
migration for Java or
PL/SQL.

If your existing application is mainly written in Java and PL/SQL and your main
concern is to minimize the code changes required to support multiple languages, then
you may want to use a Unicode database solution. If the datatypes used to stored
data remain as SQL CHAR datatypes, then the Java and PL/SQL code that accesses
these columns does not need to change.

You have evenly
distributed multilingual
data.

If the multilingual data is evenly distributed in existing schema tables and you are not
sure which tables contain multilingual data, then you should use a Unicode database
because it does not require you to identify the kind of data that is stored in each
column.

Your SQL statements and
PL/SQL code contain
Unicode data.

You must use a Unicode database. SQL statements and PL/SQL code are converted
into the database character set before being processed. If the SQL statements and
PL/SQL code contain characters that cannot be converted to the database character
set, then those characters are lost. A common place to use Unicode data in a SQL
statement is in a string literal.

You want to store
multilingual documents in
BLOB format and use
Oracle Text for content
searching.

You must use a Unicode database. The BLOB data is converted to the database
character set before being indexed by Oracle Text. If your database character set is not
UTF8, then data is lost when the documents contain characters that cannot be
converted to the database character set.

When Should You Use Unicode Datatypes?
Use Unicode datatypes in the situations described in Table 6–3.

6-8 Oracle Database Globalization Support Guide

Implementing a Unicode Solution in the Database

Table 6–3

Using Unicode Datatypes

Situation

Explanation

You want to add
multilingual support
incrementally.

If you want to add Unicode support to the existing database without migrating the
character set, then consider using Unicode datatypes to store Unicode data. You can add
columns of the SQL NCHAR datatypes to existing tables or new tables to support multiple
languages incrementally.

You want to build a
packaged application.

If you are building a packaged application to sell to customers, then you may want to
build the application using SQL NCHAR datatypes. The SQL NCHAR datatype is a reliable
Unicode datatype in which the data is always stored in Unicode, and the length of the
data is always specified in UTF-16 code units. As a result, you need to test the application
only once. The application will run on customer databases with any database character
set.

You want better
performance with
single-byte database
character sets.

If performance is your main concern, then consider using a single-byte database character
set and storing Unicode data in the SQL NCHAR datatypes.

You require UTF-16
support in Windows
clients.

If your applications are written in Visual C/C++ or Visual Basic running on Windows,
then you may want to use the SQL NCHAR datatypes. You can store UTF-16 data in SQL
NCHAR datatypes in the same way that you store it in the wchar_t buffer in Visual
C/C++ and string buffer in Visual Basic. You can avoid buffer overflow in client
applications because the length of the wchar_t and string datatypes match the length
of the SQL NCHAR datatypes in the database.

Note:

You can use a Unicode database with Unicode datatypes.

Comparing Unicode Character Sets for Database and Datatype Solutions
Oracle provides two solutions to store Unicode characters in the database: a Unicode
database solution and a Unicode datatype solution. After you select the Unicode
database solution, the Unicode datatype solution, or a combination of both, you then
determine the character set to be used in the Unicode database or the Unicode
datatype.
Table 6–4 contains advantages and disadvantages of character sets for a Unicode
database solution. The Oracle character sets that can be Unicode database character
sets are AL32UTF8, UTF8, and UTFE.

Supporting Multilingual Databases with Unicode

6-9

Implementing a Unicode Solution in the Database

Table 6–4

Character Set Advantages and Disadvantages for a Unicode Database Solution

Database
Character Set

Advantages

AL32UTF8

■

UTF8

■

UTFE

■

Supplementary characters are stored in 4
bytes, so there is no data conversion
when supplementary characters are
retrieved and inserted if the client setting
is UTF-8.
The storage for supplementary characters
requires less disk space in AL32UTF8
than in UTF8.

You can specify the length of SQL CHAR
types in number of UCS-2 code points.

Disadvantages
■

■

The binary order of the SQL CHAR
columns is always the same as the binary
order of the SQL NCHAR columns when
the data consists of the same
supplementary characters. As a result,
CHAR columns and NCHAR columns have
the same sort for identical strings.
This is the only Unicode character set for
the EBCDIC platform.

■

You can specify the length of SQL CHAR
types in number of UCS-2 code points.
The binary order of the SQL CHAR
columns is always the same as the binary
order of the SQL NCHAR columns when
the data consists of the same
supplementary characters. As a result,
CHAR columns and NCHAR columns have
the same sort for identical strings.

■

You cannot specify the length of SQL CHAR types in
number of UCS-2 code points for supplementary
characters. Supplementary characters are treated as
one code point rather than the standard two code
points.
The binary order for SQL CHAR columns is different
from the binary order of SQL NCHAR columns when
the data consists of supplementary characters. As a
result, CHAR columns and NCHAR columns do not
always have the same sort for identical strings.
Supplementary characters are stored as 6 bytes
instead of the 4 bytes defined by Unicode 4.0. As a
result, Oracle has to convert data for
supplementary characters if the client setting is
UTF-8.

Supplementary character are stored as 8 bytes (two
4-byte sequences) instead of the 5 bytes defined by
the Unicode standard. As a result, Oracle has to
convert data for those supplementary characters.
UTFE is not a standard encoding in the Unicode
standard. As a result, clients requiring standard
UTF-8 encoding must convert data from UTFE to
the standard encoding when data is retrieved and
inserted.

Table 6–5 contains advantages and disadvantages of different character sets for a
Unicode datatype solution. The Oracle character sets that can be national character sets
are AL16UTF16 and UTF8. The default is AL16UTF16.

6-10 Oracle Database Globalization Support Guide

Unicode Case Studies

Table 6–5

Character Set Advantages and Disadvantages for a Unicode Datatype Solution

National
Character Set

Advantages

AL16UTF16

■

UTF8

■

Disadvantages

Asian data in AL16UTF16 is usually more
compact than in UTF8. As a result, you save disk
space and have less disk I/O when most of the
multilingual data stored in the database is Asian
data.
It is usually faster to process strings encoded in
the AL16UTF16 character set than strings encoded
in UTF8 because Oracle processes most characters
in an AL16UTF16 encoded string as fixed-width
characters.

■

European ASCII data requires more disk
space to store in AL16UTF16 than in UTF8.
If most of your data is European data, then
it uses more disk space than if it were UTF8
data.
The maximum lengths for NCHAR and
NVARCHAR2 are 1000 and 2000 characters,
which is less than the lengths for NCHAR
(2000) and NVARCHAR2 (4000) in UTF8.

The maximum length limits for the NCHAR and
NVARCHAR2 columns are 1000 and 2000
characters, respectively. Because the data is
fixed-width, the lengths are guaranteed.
European data in UTF8 is usually more compact
than in AL16UTF16. As a result, you save disk
space and have better response time when most of
the multilingual data stored in the database is
European data.
The maximum lengths for the NCHAR and
NVARCHAR2 columns are 2000 and 4000 characters
respectively, which is more than those for NCHAR
(1000) and NVARCHAR2 (2000) in AL16UTF16.
Although the maximum lengths of the NCHAR and
NVARCHAR2 columns are larger in UTF8, the
actual storage size is still bound by the byte limits
of 2000 and 4000 bytes, respectively. For example,
you can store 4000 UTF8 characters in an
NVARCHAR2 column if all the characters are single
byte, but only 4000/3 characters if all the
characters are three bytes.

■

Asian data requires more disk space to
store in UTF8 than in AL16UTF16. If most
of your data is Asian data, then disk space
usage is not less efficient than when the
character set is AL16UTF16.
Although you can specify larger length
limits for NCHAR and NVARCHAR, you are
not guaranteed to be able to insert the
number of characters specified by these
limits. This is because UTF8 allows
variable-width characters.
It is usually slower to process strings
encoded in UTF8 than strings encoded in
AL16UTF16 because UTF8 encoded strings
consist of variable-width characters.

Unicode Case Studies
This section describes typical scenarios for storing Unicode characters in an Oracle
database:
■

Example 6–3, "Unicode Solution with a Unicode Database"

■

Example 6–4, "Unicode Solution with Unicode Datatypes"

■

Example 6–5, "Unicode Solution with a Unicode Database and Unicode Datatypes"

Example 6–3 Unicode Solution with a Unicode Database

An American company running a Java application would like to add German and
French support in the next release of the application. They would like to add Japanese
support at a later time. The company currently has the following system configuration:
■

The existing database has a database character set of US7ASCII.

■

All character data in the existing database is composed of ASCII characters.

■

PL/SQL stored procedures are used in the database.

■

The database is about 300 GB.

■

There is a nightly downtime of 4 hours.

In this case, a typical solution is to choose UTF8 for the database character set because
of the following reasons:

Supporting Multilingual Databases with Unicode

6-11

Unicode Case Studies

■

The database is very large and the scheduled downtime is short. Fast migration of
the database to Unicode is vital. Because the database is in US7ASCII, the easiest
and fastest way of enabling the database to support Unicode is to switch the
database character set to UTF8 by running the CSALTER script. No data
conversion is required because US7ASCII is a subset of UTF8.
Because most of the code is written in Java and PL/SQL, changing the database
character set to UTF8 is unlikely to break existing code. Unicode support is
automatically enabled in the application.
Because the application supports French, German, and Japanese, there are few
supplementary characters. Both AL32UTF8 and UTF8 are suitable.

Example 6–4 Unicode Solution with Unicode Datatypes

A European company that runs its applications mainly on Windows platforms wants
to add new Windows applications written in Visual C/C++. The new applications will
use the existing database to support Japanese and Chinese customer names. The
company currently has the following system configuration:
■
■

■

The existing database has a database character set of WE8ISO8859P1.
All character data in the existing database is composed of Western European
characters.
The database is around 50 GB.

A typical solution is take the following actions:
■

Use NCHAR and NVARCHAR2 datatypes to store Unicode characters

■

Keep WE8ISO8859P1 as the database character set

■

Use AL16UTF16 as the national character set

The reasons for this solution are:
■

■

Migrating the existing database to a Unicode database requires data conversion
because the database character set is WE8ISO8859P1 (a Latin-1 character set),
which is not a subset of UTF8. As a result, there will be some overhead in
converting the data to UTF8.
The additional languages are supported in new applications only. They do not
depend on the existing applications or schemas. It is simpler to use the Unicode
datatype in the new schema and keep the existing schemas unchanged.
Only customer name columns require Unicode support. Using a single NCHAR
column meets the customer's requirements without migrating the entire database.
Because the languages to be supported are mostly Asian languages, AL16UTF16
should be used as the national character set so that disk space is used more
efficiently.
The lengths of the SQL NCHAR datatypes are defined as number of characters. This
is the same as how they are treated when using wchar_t strings in Windows
C/C++ programs. This reduces programming complexity.
Existing applications using the existing schemas are unaffected.

Example 6–5 Unicode Solution with a Unicode Database and Unicode Datatypes

A Japanese company wants to develop a new Java application. The company expects
that the application will support as many languages as possible in the long run.

6-12 Oracle Database Globalization Support Guide

Designing Database Schemas to Support Multiple Languages

■

In order to store documents as is, the company decided to use the BLOB datatype
to store documents of multiple languages.
The company may also want to generate UTF-8 XML documents from the
relational data for business-to-business data exchange.
The back-end has Windows applications written in C/C++ using ODBC to access
the Oracle database.

In this case, the typical solution is to create a Unicode database using AL32UTF8 as the
database character set and use the SQL NCHAR datatypes to store multilingual data.
The national character set should be set to AL16UTF16. The reasons for this solution
are as follows:
■

■

When documents of different languages are stored in BLOB format, Oracle Text
requires the database character set to be one of the UTF-8 character sets. Because
the applications may retrieve relational data as UTF-8 XML format (where
supplementary characters are stored as four bytes), AL32UTF8 should be used as
the database character set to avoid data conversion when UTF-8 data is retrieved
or inserted.
Because applications are new and written in both Java and Windows C/C++, the
company should use the SQL NCHAR datatype for its relational data. Both Java and
Windows support the UTF-16 character datatype, and the length of a character
string is always measured in the number of characters.
If most of the data is for Asian languages, then AL16UTF16 should be used with
the SQL NCHAR datatypes because AL16UTF16 offers better storage efficiency.

Designing Database Schemas to Support Multiple Languages
In addition to choosing a Unicode solution, the following issues should be taken into
consideration when the database schema is designed to support multiple languages:
■

Specifying Column Lengths for Multilingual Data

■

Storing Data in Multiple Languages

■

Storing Documents in Multiple Languages in LOB Datatypes

■

Creating Indexes for Searching Multilingual Document Contents

Specifying Column Lengths for Multilingual Data
When you use NCHAR and NVARCHAR2 datatypes for storing multilingual data, the
column size specified for a column is defined in number of characters. (The number of
characters means the number of Unicode code units.) Table 6–6 shows the maximum
size of the NCHAR and NVARCHAR2 datatypes for the AL16UTF16 and UTF8 national
character sets.
Table 6–6

Maximum Datatype Size

National Character Set

Maximum Column Size of NCHAR Maximum Column Size of
Datatype
NVARCHAR2 Datatype

AL16UTF16

1000 characters

2000 characters

UTF8

2000 bytes

4000 bytes

When you use CHAR and VARCHAR2 datatypes for storing multilingual data, the
maximum length specified for each column is, by default, in number of bytes. If the

Supporting Multilingual Databases with Unicode

6-13

Designing Database Schemas to Support Multiple Languages

database needs to support Thai, Arabic, or multibyte languages such as Chinese and
Japanese, then the maximum lengths of the CHAR, VARCHAR, and VARCHAR2 columns
may need to be extended. This is because the number of bytes required to encode these
languages in UTF8 or AL32UTF8 may be significantly larger than the number of bytes
for encoding English and Western European languages. For example, one Thai
character in the Thai character set requires 3 bytes in UTF8 or AL32UTF8. In addition,
the maximum column lengths for CHAR, VARCHAR, and VARCHAR2 datatypes are 2000
bytes, 4000 bytes, and 4000 bytes respectively. If applications need to store more than
4000 bytes, then they should use the CLOB datatype.

Storing Data in Multiple Languages
The Unicode character set includes characters of most written languages around the
world, but it does not contain information about the language to which a given
character belongs. In other words, a character such as ä does not contain information
about whether it is a French or German character. In order to provide information in
the language a user desires, data stored in a Unicode database should accompany the
language information to which the data belongs.
There are many ways for a database schema to relate data to a language. The following
sections discuss different approaches:
■

Store Language Information with the Data

■

Select Translated Data Using Fine-Grained Access Control

Store Language Information with the Data
For data such as product descriptions or product names, you can add a language
column (language_id) of CHAR or VARCHAR2 datatype to the product table to
identify the language of the corresponding product information. This enables
applications to retrieve the information in the desired language. The possible values
for this language column are the 3-letter abbreviations of the valid NLS_LANGUAGE
values of the database.
See Also: Appendix A, "Locale Data" for a list of NLS_LANGUAGE
values and their abbreviations

You can also create a view to select the data of the current language. For example:
ALTER TABLE scott.product_information ADD (language_id VARCHAR2(50)):
CREATE OR
SELECT
FROM
WHERE

REPLACE VIEW product AS
product_id, product_name
product_information
language_id = SYS_CONTEXT('USERENV','LANG');

Select Translated Data Using Fine-Grained Access Control
Fine-grained access control enables you to limit the degree to which a user can view
information in a table or view. Typically, this is done by appending a WHERE clause.
When you add a WHERE clause as a fine-grained access policy to a table or view, Oracle
automatically appends the WHERE clause to any SQL statements on the table at run
time so that only those rows satisfying the WHERE clause can be accessed.
You can use this feature to avoid specifying the desired language of a user in the
WHERE clause in every SELECT statement in your applications. The following WHERE
clause limits the view of a table to the rows corresponding to the desired language of a
user:

6-14 Oracle Database Globalization Support Guide

Designing Database Schemas to Support Multiple Languages

WHERE language_id = SYS_CONTEXT('userenv', 'LANG')

Specify this WHERE clause as a fine-grained access policy for product_information
as follows:
CREATE FUNCTION func1 (sch VARCHAR2 , obj VARCHAR2 )
RETURN VARCHAR2(100);
BEGIN
RETURN 'language_id = SYS_CONTEXT(''userenv'', ''LANG'')';
END
/
DBMS_RLS.ADD_POLICY ('scott', 'product_information', 'lang_policy', 'scott',
'func1', 'select');

Then any SELECT statement on the product_information table automatically
appends the WHERE clause.
See Also: Oracle Database Application Developer's Guide Fundamentals for more information about fine-grained access
control

Storing Documents in Multiple Languages in LOB Datatypes
You can store documents in multiple languages in CLOB, NCLOB, or BLOB datatypes
and set up Oracle Text to enable content search for the documents.
Data in CLOB columns is stored in a format that is compatible with UCS-2 when the
database character set is multibyte, such as UTF8 or AL32UTF8. This means that the
storage space required for an English document doubles when the data is converted.
Storage for an Asian language document in a CLOB column requires less storage space
than the same document in a LONG column using UTF8, typically around 30% less,
depending on the contents of the document.
Documents in NCLOB format are also stored in a proprietary format that is compatible
with UCS-2 regardless of the database character set or national character set. The
storage space requirement is the same as for CLOB data. Document contents are
converted to UTF-16 when they are inserted into a NCLOB column. If you want to store
multilingual documents in a non-Unicode database, then choose NCLOB. However,
content search on NCLOB is not yet supported.
Documents in BLOB format are stored as they are. No data conversion occurs during
insertion and retrieval. However, SQL string manipulation functions (such as LENGTH
or SUBSTR) and collation functions (such as NLS_SORT and ORDER BY) cannot be
applied to the BLOB datatype.
Table 6–7 lists the advantages and disadvantages of the CLOB, NCLOB, and BLOB
datatypes when storing documents:

Supporting Multilingual Databases with Unicode

6-15

Designing Database Schemas to Support Multiple Languages

Table 6–7

Comparison of LOB Datatypes for Document Storage

Datatypes

Advantages

CLOB

■

Content search support

■

String manipulation support

■

NCLOB

BLOB

Disadvantages

Cannot store binary documents
No content search support

Independent of database character set

■

String manipulation support

■

Independent of database character set

■

Content search support

■

No data conversion, data stored as is

■

Data conversion is necessary for
insertion

■
■

■

Depends on database character set

Data conversion is necessary for
insertion

■

Cannot store binary documents

■

No string manipulation support

Can store binary documents such as Microsoft
Word or Microsoft Excel

Creating Indexes for Searching Multilingual Document Contents
Oracle Text enables you to build indexes for content search on multilingual documents
stored in CLOB format and BLOB format. It uses a language-specific lexer to parse the
CLOB or BLOB data and produces a list of searchable keywords.
Create a multilexer to search multilingual documents. The multilexer chooses a
language-specific lexer for each row, based on a language column. This section
describes the high level steps to create indexes for documents in multiple languages. It
contains the following topics:
■

Creating Multilexers

■

Creating Indexes for Documents Stored in the CLOB Datatype

■

Creating Indexes for Documents Stored in the BLOB Datatype
See Also:

Oracle Text Reference

Creating Multilexers
The first step in creating the multilexer is the creation of language-specific lexer
preferences for each language supported. The following example creates English,
German, and Japanese lexers with PL/SQL procedures:
ctx_ddl.create_preference('english_lexer', 'basic_lexer');
ctx_ddl.set_attribute('english_lexer','index_themes','yes');
ctx_ddl.create_preference('german_lexer', 'basic_lexer');
ctx_ddl.set_attribute('german_lexer','composite','german');
ctx_ddl.set_attribute('german_lexer','alternate_spelling','german');
ctx_ddl.set_attribute('german_lexer','mixed_case','yes');
ctx_ddl.create_preference('japanese_lexer', 'JAPANESE_VGRAM_LEXER');

After the language-specific lexer preferences are created, they need to be gathered
together under a single multilexer preference. First, create the multilexer preference,
using the MULTI_LEXER object:
ctx_ddl.create_preference('global_lexer','multi_lexer');

Now add the language-specific lexers to the multilexer preference using the add_
sub_lexer call:
6-16 Oracle Database Globalization Support Guide

Designing Database Schemas to Support Multiple Languages

ctx_ddl.add_sub_lexer('global_lexer', 'german', 'german_lexer');
ctx_ddl.add_sub_lexer('global_lexer', 'japanese', 'japanese_lexer');
ctx_ddl.add_sub_lexer('global_lexer', 'default','english_lexer');

This nominates the german_lexer preference to handle German documents, the
japanese_lexer preference to handle Japanese documents, and the english_
lexer preference to handle everything else, using DEFAULT as the language.

Creating Indexes for Documents Stored in the CLOB Datatype
The multilexer decides which lexer to use for each row based on a language column in
the table. This is a character column that stores the language of the document in a text
column. Use the Oracle language name to identify the language of a document in this
column. For example, if you use the CLOB datatype to store your documents, then add
the language column to the table where the documents are stored:
CREATE TABLE globaldoc
(doc_id
NUMBER
PRIMARY KEY,
language VARCHAR2(30),
text
CLOB);

To create an index for this table, use the multilexer preference and specify the name of
the language column:
CREATE INDEX globalx ON globaldoc(text)
indextype IS ctxsys.context
parameters ('lexer
global_lexer
language
column
language');

Creating Indexes for Documents Stored in the BLOB Datatype
In addition to the language column, the character set and format columns must be
added in the table where the documents are stored. The character set column stores the
character set of the documents using the Oracle character set names. The format
column specifies whether a document is a text or binary document. For example, the
CREATE TABLE statement can specify columns called characterset and format:
CREATE TABLE globaldoc (
doc_id
NUMBER
PRIMARY KEY,
language
VARCHAR2(30),
characterset VARCHAR2(30),
format
VARCHAR2(10),
text
BLOB
);

You can put word-processing or spreadsheet documents into the table and specify
binary in the format column. For documents in HTML, XML and text format, you
can put them into the table and specify text in the format column.
Because there is a column in which to specify the character set, you can store text
documents in different character sets.
When you create the index, specify the names of the format and character set columns:
CREATE INDEX globalx ON globaldoc(text)
indextype is ctxsys.context
parameters ('filter inso_filter
lexer global_lexer
language column language
Supporting Multilingual Databases with Unicode

6-17

Designing Database Schemas to Support Multiple Languages

format column format
charset column characterset');

You can use the charset_filter if all documents are in text format. The charset_
filter converts data from the character set specified in the charset column to the
database character set.

6-18 Oracle Database Globalization Support Guide

7
Programming with Unicode
This chapter describes how to use programming and access products for Oracle
Database with Unicode. This chapter contains the following topics:
■

Overview of Programming with Unicode

■

SQL and PL/SQL Programming with Unicode

■

OCI Programming with Unicode

■

Pro*C/C++ Programming with Unicode

■

JDBC Programming with Unicode

■

ODBC and OLE DB Programming with Unicode

■

XML Programming with Unicode

Overview of Programming with Unicode
Oracle offers several database access products for inserting and retrieving Unicode
data. Oracle offers database access products for commonly used programming
environments such as Java and C/C++. Data is transparently converted between the
database and client programs, which ensures that client programs are independent of
the database character set and national character set. In addition, client programs are
sometimes even independent of the character datatype, such as NCHAR or CHAR, used
in the database.
To avoid overloading the database server with data conversion operations, Oracle
always tries to move them to the client side database access products. In a few cases,
data must be converted in the database, which affects performance. This chapter
discusses details of the data conversion paths.

Database Access Product Stack and Unicode
Oracle offers a comprehensive set of database access products that enable programs
from different development environments to access Unicode data stored in the
database. These products are listed in Table 7–1.

Programming with Unicode

7-1

Overview of Programming with Unicode

Table 7–1

Oracle Database Access Products

Programming
Environment

Oracle Database Access Products

C/C++

Oracle Call Interface (OCI)
Oracle Pro*C/C++
Oracle ODBC driver
Oracle Provider for OLE DB
Oracle Data Provider for .NET

Java

Oracle JDBC OCI or thin driver
Oracle server-side thin driver
Oracle server-side internal driver

PL/SQL

Oracle PL/SQL and SQL

Visual Basic/C#

Oracle ODBC driver
Oracle Provider for OLE DB

Figure 7–1 shows how the database access products can access the database.
Figure 7–1 Oracle Database Access Products
· Visual Basic Programs
· VBScript using ADO
· C#
· ASP
· OLE DB
· ODBC
· Oracle Data Provider
for .NET

C/C++ Programs
Java Programs

Pro*C/C++
JDBC

Oracle Call Interface (OCI)

Thin

Oracle
Net
PL/SQL

Oracle

SQL

Oracle Net on TCP/IP

Java

The Oracle Call Interface (OCI) is the lowest level API that the rest of the client-side
database access products use. It provides a flexible way for C/C++ programs to access
Unicode data stored in SQL CHAR and NCHAR datatypes. Using OCI, you can
programmatically specify the character set (UTF-8, UTF-16, and others) for the data to
be inserted or retrieved. It accesses the database through Oracle Net.
Oracle Pro*C/C++ enables you to embed SQL and PL/SQL in your programs. It uses
OCI's Unicode capabilities to provide UTF-16 and UTF-8 data access for SQL CHAR
and NCHAR datatypes.
The Oracle ODBC driver enables C/C++, Visual Basic, and VBScript programs
running on Windows platforms to access Unicode data stored in SQL CHAR and NCHAR
datatypes of the database. It provides UTF-16 data access by implementing the
SQLWCHAR interface specified in the ODBC standard specification.
The Oracle Provider for OLE DB enables C/C++, Visual Basic, and VBScript programs
running on Windows platforms to access Unicode data stored in SQL CHAR and NCHAR
datatypes. It provides UTF-16 data access through wide string OLE DB datatypes.

7-2 Oracle Database Globalization Support Guide

SQL and PL/SQL Programming with Unicode

The Oracle Data Provider for .NET enables programs running in any .NET
programming environment on Windows platforms to access Unicode data stored in
SQL CHAR and NCHAR datatypes. It provides UTF-16 data access through Unicode
datatypes.
Oracle JDBC drivers are the primary Java programmatic interface for accessing an
Oracle database. Oracle provides the following JDBC drivers:
■

■

The JDBC OCI driver that is used by Java applications and requires the OCI
library
The JDBC thin driver, which is a pure Java driver that is primarily used by Java
applets and supports the Oracle Net protocol over TCP/IP
The JDBC server-side thin driver, a pure Java driver used inside Java stored
procedures to connect to another Oracle server
The JDBC server-side internal driver that is used inside the Oracle server to access
the data in the database

All drivers support Unicode data access to SQL CHAR and NCHAR datatypes in the
database.
The PL/SQL and SQL engines process PL/SQL programs and SQL statements on
behalf of client-side programs such as OCI and server-side PL/SQL stored procedures.
They allow PL/SQL programs to declare CHAR, VARCHAR2, NCHAR, and NVARCHAR2
variables and to access SQL CHAR and NCHAR datatypes in the database.
The following sections describe how each of the database access products supports
Unicode data access to an Oracle database and offer examples for using those
products:
■

SQL and PL/SQL Programming with Unicode

■

OCI Programming with Unicode

■

Pro*C/C++ Programming with Unicode

■

JDBC Programming with Unicode

■

ODBC and OLE DB Programming with Unicode

SQL and PL/SQL Programming with Unicode
SQL is the fundamental language with which all programs and users access data in an
Oracle database either directly or indirectly. PL/SQL is a procedural language that
combines the data manipulating power of SQL with the data processing power of
procedural languages. Both SQL and PL/SQL can be embedded in other programming
languages. This section describes Unicode-related features in SQL and PL/SQL that
you can deploy for multilingual applications.
This section contains the following topics:
■

SQL NCHAR Datatypes

■

Implicit Datatype Conversion Between NCHAR and Other Datatypes

■

Exception Handling for Data Loss During Datatype Conversion

■

Rules for Implicit Datatype Conversion

■

SQL Functions for Unicode Datatypes

■

Other SQL Functions

Programming with Unicode

7-3

SQL and PL/SQL Programming with Unicode

■

Unicode String Literals

■

Using the UTL_FILE Package with NCHAR Data
See Also:
■

Oracle Database SQL Reference

■

PL/SQL User's Guide and Reference

SQL NCHAR Datatypes
There are three SQL NCHAR datatypes:
■

The NCHAR Datatype

■

The NVARCHAR2 Datatype

■

The NCLOB Datatype

The NCHAR Datatype
When you define a table column or a PL/SQL variable as the NCHAR datatype, the
length is always specified as the number of characters. For example, the following
statement creates a column with a maximum length of 30 characters:
CREATE TABLE table1 (column1 NCHAR(30));

The maximum number of bytes for the column is determined as follows:
maximum number of bytes = (maximum number of characters) x (maximum number of
bytes for each character)

For example, if the national character set is UTF8, then the maximum byte length is 30
characters times 3 bytes for each character, or 90 bytes.
The national character set, which is used for all NCHAR datatypes, is defined when the
database is created. The national character set can be either UTF8 or AL16UTF16. The
default is AL16UTF16.
The maximum column size allowed is 2000 characters when the national character set
is UTF8 and 1000 when it is AL16UTF16. The actual data is subject to the maximum
byte limit of 2000. The two size constraints must be satisfied at the same time. In
PL/SQL, the maximum length of NCHAR data is 32767 bytes. You can define an NCHAR
variable of up to 32767 characters, but the actual data cannot exceed 32767 bytes. If
you insert a value that is shorter than the column length, then Oracle pads the value
with blanks to whichever length is smaller: maximum character length or maximum
byte length.
UTF8 may affect performance because it is a variable-width
character set. Excessive blank padding of NCHAR fields decreases
performance. Consider using the NVARCHAR datatype or changing
to the AL16UTF16 character set for the NCHAR datatype.

Note:

The NVARCHAR2 Datatype
The NVARCHAR2 datatype specifies a variable length character string that uses the
national character set. When you create a table with an NVARCHAR2 column, you
specify the maximum number of characters for the column. Lengths for NVARCHAR2
are always in units of characters, just as for NCHAR. Oracle subsequently stores each

7-4 Oracle Database Globalization Support Guide

SQL and PL/SQL Programming with Unicode

value in the column exactly as you specify it, if the value does not exceed the column's
maximum length. Oracle does not pad the string value to the maximum length.
The maximum column size allowed is 4000 characters when the national character set
is UTF8 and 2000 when it is AL16UTF16. The maximum length of an NVARCHAR2
column in bytes is 4000. Both the byte limit and the character limit must be met, so the
maximum number of characters that is actually allowed in an NVARCHAR2 column is
the number of characters that can be written in 4000 bytes.
In PL/SQL, the maximum length for an NVARCHAR2 variable is 32767 bytes. You can
define NVARCHAR2 variables up to 32767 characters, but the actual data cannot exceed
32767 bytes.
The following statement creates a table with one NVARCHAR2 column whose
maximum length in characters is 2000 and maximum length in bytes is 4000.
CREATE TABLE table2 (column2 NVARCHAR2(2000));

The NCLOB Datatype
NCLOB is a character large object containing Unicode characters, with a maximum size
of 4 gigabytes. Unlike the BLOB datatype, the NCLOB datatype has full transactional
support so that changes made through SQL, the DBMS_LOB package, or OCI
participate fully in transactions. Manipulations of NCLOB value can be committed and
rolled back. Note, however, that you cannot save an NCLOB locator in a PL/SQL or
OCI variable in one transaction and then use it in another transaction or session.
NCLOB values are stored in the database in a format that is compatible with UCS-2,
regardless of the national character set. Oracle translates the stored Unicode value to
the character set requested on the client or on the server, which can be fixed-width or
variable-width. When you insert data into an NCLOB column using a variable-width
character set, Oracle converts the data into a format that is compatible with UCS-2
before storing it in the database.
See Also: Oracle Database Application Developer's Guide - Large
Objects for more information about the NCLOB datatype

Implicit Datatype Conversion Between NCHAR and Other Datatypes
Oracle supports implicit conversions between SQL NCHAR datatypes and other Oracle
datatypes, such as CHAR, VARCHAR2, NUMBER, DATE, ROWID, and CLOB. Any implicit
conversions for CHAR and VARCHAR2 datatypes are also supported for SQL NCHAR
datatypes. You can use SQL NCHAR datatypes the same way as SQL CHAR datatypes.
Type conversions between SQL CHAR datatypes and SQL NCHAR datatypes may
involve character set conversion when the database and national character sets are
different. Padding with blanks may occur if the target data is either CHAR or NCHAR.
See Also:

Oracle Database SQL Reference

Exception Handling for Data Loss During Datatype Conversion
Data loss can occur during datatype conversion when character set conversion is
necessary. If a character in the source character set is not defined in the target character
set, then a replacement character is used in its place. For example, if you try to insert
NCHAR data into a regular CHAR column and the character data in NCHAR (Unicode)
form cannot be converted to the database character set, then the character is replaced
by a replacement character defined by the database character set. The NLS_NCHAR_
CONV_EXCP initialization parameter controls the behavior of data loss during

Programming with Unicode

7-5

SQL and PL/SQL Programming with Unicode

character type conversion. When this parameter is set to TRUE, any SQL statements
that result in data loss return an ORA-12713 error and the corresponding operation is
stopped. When this parameter is set to FALSE, data loss is not reported and the
unconvertible characters are replaced with replacement characters. The default value
is TRUE. This parameter works for both implicit and explicit conversion.
In PL/SQL, when data loss occurs during conversion of SQL CHAR and NCHAR
datatypes, the LOSSY_CHARSET_CONVERSION exception is raised for both implicit
and explicit conversion.

Rules for Implicit Datatype Conversion
In some cases, conversion between datatypes is possible in only one direction. In other
cases, conversion in both directions is possible. Oracle defines a set of rules for
conversion between datatypes. Table 7–2 contains the rules for conversion between
datatypes.
Table 7–2

Rules for Conversion Between Datatypes

Statement

Rule

INSERT/UPDATE
statement

Values are converted to the datatype of the target database column.

SELECT INTO statement Data from the database is converted to the datatype of the target variable.
Variable assignments

Values on the right of the equal sign are converted to the datatype of the target variable
on the left of the equal sign.

Parameters in SQL and
PL/SQL functions

CHAR, VARCHAR2, NCHAR, and NVARCHAR2 are loaded the same way. An argument with
a CHAR, VARCHAR2, NCHAR or NVARCHAR2 datatype is compared to a formal parameter
of any of the CHAR, VARCHAR2, NCHAR or NVARCHAR2 datatypes. If the argument and
formal parameter datatypes do not match exactly, then implicit conversions are
introduced when data is copied into the parameter on function entry and copied out to
the argument on function exit.

Concatenation ||
operation or CONCAT
function

If one operand is a SQL CHAR or NCHAR datatype and the other operand is a NUMBER or
other non-character datatype, then the other datatype is converted to VARCHAR2 or
NVARCHAR2. For concatenation between character datatypes, see "SQL NCHAR datatypes
and SQL CHAR datatypes" on page 7-7.

SQL CHAR or NCHAR
datatypes and NUMBER
datatype

Character values are converted to NUMBER datatype.

7-6 Oracle Database Globalization Support Guide

SQL and PL/SQL Programming with Unicode

Table 7–2 (Cont.) Rules for Conversion Between Datatypes
Statement

Rule

SQL CHAR or NCHAR
datatypes and DATE
datatype

Character values are converted to DATE datatype.

SQL CHAR or NCHAR
datatypes and ROWID
datatype

Character values are converted to ROWID datatype.

SQL NCHAR datatypes
and SQL CHAR
datatypes

Comparisons between SQL NCHAR datatypes and SQL CHAR datatypes are more
complex because they can be encoded in different character sets.
When CHAR and VARCHAR2 values are compared, the CHAR values are converted to
VARCHAR2 values.
When NCHAR and NVARCHAR2 values are compared, the NCHAR values are converted to
NVARCHAR2 values.
When there is comparison between SQL NCHAR datatypes and SQL CHAR datatypes,
character set conversion occurs if they are encoded in different character sets. The
character set for SQL NCHAR datatypes is always Unicode and can be either UTF8 or
AL16UTF16 encoding, which have the same character repertoires but are different
encodings of the Unicode standard. SQL CHAR datatypes use the database character set,
which can be any character set that Oracle supports. Unicode is a superset of any
character set supported by Oracle, so SQL CHAR datatypes can always be converted to
SQL NCHAR datatypes without data loss.

SQL Functions for Unicode Datatypes
SQL NCHAR datatypes can be converted to and from SQL CHAR datatypes and other
datatypes using explicit conversion functions. The examples in this section use the
table created by the following statement:
CREATE TABLE customers
(id NUMBER, name NVARCHAR2(50), address NVARCHAR2(200), birthdate DATE);
Example 7–1 Populating the Customers Table Using the TO_NCHAR Function

The TO_NCHAR function converts the data at run time, while the N function converts
the data at compilation time.
INSERT INTO customers VALUES (1000,
TO_NCHAR('John Smith'),N'500 Oracle Parkway',sysdate);
Example 7–2 Selecting from the Customer Table Using the TO_CHAR Function

The following statement converts the values of name from characters in the national
character set to characters in the database character set before selecting them according
to the LIKE clause:
SELECT name FROM customers WHERE TO_CHAR(name) LIKE '%Sm%';

You should see the following output:
NAME
-------------------------------------John Smith
Example 7–3 Selecting from the Customer Table Using the TO_DATE Function

Using the N function shows that either NCHAR or CHAR data can be passed as
parameters for the TO_DATE function. The datatypes can mixed because they are
converted at run time.

Programming with Unicode

7-7

SQL and PL/SQL Programming with Unicode

DECLARE
ndatestring NVARCHAR2(20) := N'12-SEP-1975';
ndstr NVARCHAR2(50);
BEGIN
SELECT name INTO ndstr FROM customers
WHERE (birthdate)> TO_DATE(ndatestring, 'DD-MON-YYYY', N'NLS_DATE_LANGUAGE =
AMERICAN');
END;

As demonstrated in Example 7–3, SQL NCHAR data can be passed to explicit
conversion functions. SQL CHAR and NCHAR data can be mixed together when using
multiple string parameters.
Oracle Database SQL Reference for more information
about explicit conversion functions for SQL NCHAR datatypes

See Also:

Other SQL Functions
Most SQL functions can take arguments of SQL NCHAR datatypes as well as mixed
character datatypes. The return datatype is based on the type of the first argument. If a
non-string datatype like NUMBER or DATE is passed to these functions, then it is
converted to VARCHAR2. The following examples use the customer table created in
"SQL Functions for Unicode Datatypes" on page 7-7.
Example 7–4 INSTR Function

In this example, the string literal 'Sm' is converted to NVARCHAR2 and then scanned
by INSTR, to detect the position of the first occurrence of this string in name.
SELECT INSTR(name, N'Sm', 1, 1) FROM customers;
Example 7–5 CONCAT Function
SELECT CONCAT(name,id) FROM customers;

id is converted to NVARCHAR2 and then concatenated with name.
Example 7–6 RPAD Function
SELECT RPAD(name,100,' ') FROM customers;

The following output results:
RPAD(NAME,100,'')
-----------------------------------------John Smith

The space character ' ' is converted to the corresponding character in the NCHAR
character set and then padded to the right of name until the total display length
reaches 100.
See Also:

Oracle Database SQL Reference

Unicode String Literals
You can input Unicode string literals in SQL and PL/SQL as follows:
■

Put a prefix N before a string literal that is enclosed with single quote marks. This
explicitly indicates that the following string literal is an NCHAR string literal. For

7-8 Oracle Database Globalization Support Guide

SQL and PL/SQL Programming with Unicode

example, N'résumé' is an NCHAR string literal. For information about limitations
of this method, see NCHAR String Literal Replacement on page 7-9.
■

Use the NCHR(n) SQL function, which returns a unit of character code in the
national character set, which is AL16UTF16 or UTF8. The result of concatenating
several NCHR(n) functions is NVARCHAR2 data. In this way, you can bypass the
client and server character set conversions and create an NVARCHAR2 string
directly. For example, NCHR(32) represents a blank character.
Because NCHR(n) is associated with the national character set, portability of the
resulting value is limited to applications that run with the same national character
set. If this is a concern, then use the UNISTR function to remove portability
limitations.

■

Use the UNISTR('string') SQL function. UNISTR('string') converts a string to
the national character set. To ensure portability and to preserve data, include only
ASCII characters and Unicode encoding in the following form: \xxxx, where
xxxx is the hexadecimal value of a character code value in UTF-16 encoding
format. For example, UNISTR('G\0061ry') represents 'Gary'. The ASCII
characters are converted to the database character set and then to the national
character set. The Unicode encoding is converted directly to the national character
set.

The last two methods can be used to encode any Unicode string literals.

NCHAR String Literal Replacement
This section provides information on how to avoid data loss when performing NCHAR
string literal replacement.
Being part of a SQL or PL/SQL statement, the text of any literal, with or without the
prefix N, is encoded in the same character set as the rest of the statement. On the client
side, the statement is in the client character set, which is determined by the client
character set defined in NLS_LANG, or specified in the OCIEnvNlsCreate() call, or
predefined as UTF-16 in JDBC. On the server side the statement is in the database
character set.
■

When the SQL or PL/SQL statement is transferred from client to the database
server, its character set is converted accordingly. It is important to note that if the
database character set does not contain all characters used in the text literals, then
the data is lost in this conversion. This problem affects NCHAR string literals more
than the CHAR text literals. This is because the N' literals are designed to be
independent of the database charactser set, and should be able to provide any data
that the client character set supports.
To avoid data loss in conversion to an incompatible database character set, you can
activate the NCHAR literal replacement functionality. The functionality
transparently replaces the N' literals on the client side with an internal format. The
database server then decodes this to Unicode when the statement is executed.

■

The sections "Handling SQL NCHAR String Literals in OCI" on page 7-16 and
"Using SQL NCHAR String Literals in JDBC" on page 7-22 show how to switch on
the replacement functionality in OCI and JDBC, respectively. Because many
applications, for example, SQL*Plus, use OCI to connect to a database, and they do
not control NCHAR literal replacement explicitly, you can set the client environment
variable ORA_NCHAR_LITERAL_REPLACE to TRUE to control the functionality for
them. By default, the functionality is switched off to maintain backward
compatibility.

Programming with Unicode

7-9

OCI Programming with Unicode

Using the UTL_FILE Package with NCHAR Data
The UTL_FILE package handles Unicode national character set data. The functions
and procedures include the following:
■

FOPEN_NCHAR
This function opens a file in Unicode for input or output, with the maximum line
size specified. With this function, you can read or write a text file in Unicode
instead of in the database character set.

■

GET_LINE_NCHAR
This procedure reads text from the open file identified by the file handle and
places the text in the output buffer parameter. With this procedure, you can read a
text file in Unicode instead of in the database character set.

■

PUT_NCHAR
This procedure writes the text string stored in the buffer parameter to the open file
identified by the file handle. With this procedure, you can write a text file in
Unicode instead of in the database character set.

■

PUT_LINE_NCHAR
This procedure writes the text string stored in the buffer parameter to the open file
identified by the file handle. With this procedure, you can write a text file in
Unicode instead of in the database character set.

■

PUTF_NCHAR
This procedure is a formatted PUT_NCHAR procedure. With this procedure, you
can write a text file in Unicode instead of in the database character set.
See Also: PL/SQL Packages and Types Reference for more
information about the UTL_FILE package

OCI Programming with Unicode
OCI is the lowest-level API for accessing a database, so it offers the best possible
performance. When using Unicode with OCI, consider these topics:
■

OCIEnvNlsCreate() Function for Unicode Programming

■

OCI Unicode Code Conversion

■

Setting UTF-8 to the NLS_LANG Character Set in OCI

■

Binding and Defining SQL CHAR Datatypes in OCI

■

Binding and Defining SQL NCHAR Datatypes in OCI

■

Binding and Defining CLOB and NCLOB Unicode Data in OCI
See Also: Chapter 10, "OCI Programming in a Global
Environment"

OCIEnvNlsCreate() Function for Unicode Programming
The OCIEnvNlsCreate() function is used to specify a SQL CHAR character set and a
SQL NCHAR character set when the OCI environment is created. It is an enhanced
version of the OCIEnvCreate() function and has extended arguments for two
character set IDs. The OCI_UTF16ID UTF-16 character set ID replaces the Unicode
mode introduced in Oracle9i release 1 (9.0.1). For example:

7-10 Oracle Database Globalization Support Guide

OCI Programming with Unicode

OCIEnv *envhp;
status = OCIEnvNlsCreate((OCIEnv **)&envhp,
(ub4)0,
(void *)0,
(void *(*) ()) 0,
(void *(*) ()) 0,
(void(*) ()) 0,
(size_t) 0,
(void **)0,
(ub2)OCI_UTF16ID, /* Metadata and SQL CHAR character set */
(ub2)OCI_UTF16ID /* SQL NCHAR character set */);

The Unicode mode, in which the OCI_UTF16 flag is used with the OCIEnvCreate()
function, is deprecated.
When OCI_UTF16ID is specified for both SQL CHAR and SQL NCHAR character sets, all
metadata and bound and defined data are encoded in UTF-16. Metadata includes SQL
statements, user names, error messages, and column names. Thus, all inherited
operations are independent of the NLS_LANG setting, and all metatext data parameters
(text*) are assumed to be Unicode text datatypes (utext*) in UTF-16 encoding.
To prepare the SQL statement when the OCIEnv() function is initialized with the
OCI_UTF16ID character set ID, call the OCIStmtPrepare() function with a
(utext*) string. The following example runs on the Windows platform only. You
may need to change wchar_t datatypes for other platforms.
const wchar_t sqlstr[] = L"SELECT * FROM ENAME=:ename";
...
OCIStmt* stmthp;
sts = OCIHandleAlloc(envh, (void **)&stmthp, OCI_HTYPE_STMT, 0,
NULL);
status = OCIStmtPrepare(stmthp, errhp,(const text*)sqlstr,
wcslen(sqlstr), OCI_NTV_SYNTAX, OCI_DEFAULT);

To bind and define data, you do not have to set the OCI_ATTR_CHARSET_ID attribute
because the OCIEnv() function has already been initialized with UTF-16 character set
IDs. The bind variable names also must be UTF-16 strings.
/* Inserting Unicode data */
OCIBindByName(stmthp1, &bnd1p, errhp, (const text*)L":ename",
(sb4)wcslen(L":ename"),
(void *) ename, sizeof(ename), SQLT_STR, (void
*)&insname_ind,
(ub2 *) 0, (ub2 *) 0, (ub4) 0, (ub4 *)0,
OCI_DEFAULT);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *)
&ename_col_len,
(ub4) 0, (ub4)OCI_ATTR_MAXDATA_SIZE, errhp);
...
/* Retrieving Unicode data */
OCIDefineByPos (stmthp2, &dfn1p, errhp, (ub4)1, (void *)ename,
(sb4)sizeof(ename), SQLT_STR, (void *)0, (ub2 *)0,
(ub2*)0, (ub4)OCI_DEFAULT);

The OCIExecute() function performs the operation.
See Also:

"Specifying Character Sets in OCI" on page 10-2

Programming with Unicode 7-11

OCI Programming with Unicode

OCI Unicode Code Conversion
Unicode character set conversions take place between an OCI client and the database
server if the client and server character sets are different. The conversion occurs on
either the client or the server depending on the circumstances, but usually on the client
side.

Data Integrity
You can lose data during conversion if you call an OCI API inappropriately. If the
server and client character sets are different, then you can lose data when the
destination character set is a smaller set than the source character set. You can avoid
this potential problem if both character sets are Unicode character sets (for example,
UTF8 and AL16UTF16).
When you bind or define SQL NCHAR datatypes, you should set the OCI_ATTR_
CHARSET_FORM attribute to SQLCS_NCHAR. Otherwise, you can lose data because the
data is converted to the database character set before converting to or from the
national character set. This occurs only if the database character set is not Unicode.

OCI Performance Implications When Using Unicode
Redundant data conversions can cause performance degradation in your OCI
applications. These conversions occur in two cases:
■

■

When you bind or define SQL CHAR datatypes and set the OCI_ATTR_CHARSET_
FORM attribute to SQLCS_NCHAR, data conversions take place from client character
set to the national database character set, and from the national character set to the
database character set. No data loss is expected, but two conversions happen, even
though it requires only one.
When you bind or define SQL NCHAR datatypes and do not set OCI_ATTR_
CHARSET_FORM, data conversions take place from client character set to the
database character set, and from the database character set to the national database
character set. In the worst case, data loss can occur if the database character set is
smaller than the client's.

To avoid performance problems, you should always set OCI_ATTR_CHARSET_FORM
correctly, based on the datatype of the target columns. If you do not know the target
datatype, then you should set the OCI_ATTR_CHARSET_FORM attribute to SQLCS_
NCHAR when binding and defining.
Table 7–3 contains information about OCI character set conversions.

7-12 Oracle Database Globalization Support Guide

OCI Programming with Unicode

Table 7–3

OCI Character Set Conversions

OCI_ATTR_
Datatypes for
CHARSET_
OCI Client Buffer FORM

Datatypes of the
Target Column in
the Database

utext

SQLCS_
IMPLICIT

utext

Conversion Between

Comments

CHAR,
VARCHAR2,
CLOB

UTF-16 and database
character set in OCI

No unexpected data loss

SQLCS_
NCHAR

NCHAR,
NVARCHAR2,
NCLOB

UTF-16 and national
character set in OCI

No unexpected data loss

SQLCS_
NCHAR

CHAR,
VARCHAR2,
CLOB

UTF-16 and national
character set in OCI

No unexpected data loss,
but may degrade
performance because the
conversion goes through the
national character set

NCHAR,
NVARCHAR2,
NCLOB

UTF-16 and database
character set in OCI

SQLCS_
IMPLICIT

National character set and
database character set in
database server

Database character set and
national character set in
database server

Data loss may occur if the
database character set is not
Unicode

text

SQLCS_
IMPLICIT

CHAR,
VARCHAR2,
CLOB

NLS_LANG character set
and database character set
in OCI

No unexpected data loss

text

SQLCS_
NCHAR

NCHAR,
NVARCHAR2,NCLOB

NLS_LANG character set
and national character set
in OCI

No unexpected data loss

text

SQLCS_
NCHAR

CHAR,
VARCHAR2,
CLOB

NLS_LANG character set
and national character set
in OCI

No unexpected data loss,
but may degrade
performance because the
conversion goes through the
national character set

National character set and
database character set in
database server
text

SQLCS_
IMPLICIT

NCHAR,
NVARCHAR2,NCLOB

NLS_LANG character set
and database character set
in OCI

Data loss may occur because
the conversion goes through
the database character set

Database character set and
national character set in
database server

OCI Unicode Data Expansion
Data conversion can result in data expansion, which can cause a buffer to overflow.
For binding operations, you need to set the OCI_ATTR_MAXDATA_SIZE attribute to a
large enough size to hold the expanded data on the server. If this is difficult to do, then
you need to consider changing the table schema. For defining operations, client
applications need to allocate enough buffer space for the expanded data. The size of
the buffer should be the maximum length of the expanded data. You can estimate the
maximum buffer length with the following calculation:
1.

Get the column data byte size.

Multiply it by the maximum number of bytes for each character in the client
character set.

Programming with Unicode 7-13

OCI Programming with Unicode

This method is the simplest and quickest way, but it may not be accurate and can
waste memory. It is applicable to any character set combination. For example, for
UTF-16 data binding and defining, the following example calculates the client buffer:
ub2 csid = OCI_UTF16ID;
oratext *selstmt = "SELECT ename FROM emp";
counter = 1;
...
OCIStmtPrepare(stmthp, errhp, selstmt, (ub4)strlen((char*)selstmt),
OCI_NTV_SYNTAX, OCI_DEFAULT);
OCIStmtExecute ( svchp, stmthp, errhp, (ub4)0, (ub4)0,
(CONST OCISnapshot*)0, (OCISnapshot*)0,
OCI_DESCRIBE_ONLY);
OCIParamGet(stmthp, OCI_HTYPE_STMT, errhp, &myparam, (ub4)counter);
OCIAttrGet((void*)myparam, (ub4)OCI_DTYPE_PARAM, (void*)&col_width,
(ub4*)0, (ub4)OCI_ATTR_DATA_SIZE, errhp);
...
maxenamelen = (col_width + 1) * sizeof(utext);
cbuf = (utext*)malloc(maxenamelen);
...
OCIDefineByPos(stmthp, &dfnp, errhp, (ub4)1, (void *)cbuf,
(sb4)maxenamelen, SQLT_STR, (void *)0, (ub2 *)0,
(ub2*)0, (ub4)OCI_DEFAULT);
OCIAttrSet((void *) dfnp, (ub4) OCI_HTYPE_DEFINE, (void *) &csid,
(ub4) 0, (ub4)OCI_ATTR_CHARSET_ID, errhp);
OCIStmtFetch(stmthp, errhp, 1, OCI_FETCH_NEXT, OCI_DEFAULT);
...

Setting UTF-8 to the NLS_LANG Character Set in OCI
For OCI client applications that support Unicode UTF-8 encoding, use AL32UTF8 to
specify the NLS_LANG character set, unless the database character set is UTF8. Use
UTF8 if the database character set is UTF8.
Do not set NLS_LANG to AL16UTF16, because AL16UTF16 is the national character set
for the server. If you need to use UTF-16, then you should specify the client character
set to OCI_UTF16ID, using the OCIAttrSet() function when binding or defining
data

Binding and Defining SQL CHAR Datatypes in OCI
To specify a Unicode character set for binding and defining data with SQL CHAR
datatypes, you may need to call the OCIAttrSet() function to set the appropriate
character set ID after OCIBind() or OCIDefine() APIs. There are two typical cases:
■

Call OCIBind() or OCIDefine() followed by OCIAttrSet() to specify UTF-16
Unicode character set encoding. For example:
...
ub2 csid = OCI_UTF16ID;
utext ename[100]; /* enough buffer for ENAME */
...
/* Inserting Unicode data */
OCIBindByName(stmthp1, &bnd1p, errhp, (oratext*)":ENAME",
(sb4)strlen((char *)":ENAME"), (void *) ename, sizeof(ename),
SQLT_STR, (void *)&insname_ind, (ub2 *) 0, (ub2 *) 0, (ub4) 0,
(ub4 *)0, OCI_DEFAULT);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *) &csid,
(ub4) 0, (ub4)OCI_ATTR_CHARSET_ID, errhp);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *) &ename_col_len,

7-14 Oracle Database Globalization Support Guide

OCI Programming with Unicode

(ub4) 0, (ub4)OCI_ATTR_MAXDATA_SIZE, errhp);
...
/* Retrieving Unicode data */
OCIDefineByPos (stmthp2, &dfn1p, errhp, (ub4)1, (void *)ename,
(sb4)sizeof(ename), SQLT_STR, (void *)0, (ub2 *)0,
(ub2*)0, (ub4)OCI_DEFAULT);
OCIAttrSet((void *) dfn1p, (ub4) OCI_HTYPE_DEFINE, (void *) &csid,
(ub4) 0, (ub4)OCI_ATTR_CHARSET_ID, errhp);
...

If bound buffers are of the utext datatype, then you should add a cast (text*)
when OCIBind() or OCIDefine() is called. The value of the OCI_ATTR_
MAXDATA_SIZE attribute is usually determined by the column size of the server
character set because this size is only used to allocate temporary buffer space for
conversion on the server when you perform binding operations.
■

Call OCIBind() or OCIDefine() with the NLS_LANG character set specified as
UTF8 or AL32UTF8.
UTF8 or AL32UTF8 can be set in the NLS_LANG environment variable. You call
OCIBind() and OCIDefine() in exactly the same manner as when you are not
using Unicode. Set the NLS_LANG environment variable to UTF8 or AL32UTF8
and run the following OCI program:
...
oratext ename[100]; /* enough buffer size for ENAME */
...
/* Inserting Unicode data */
OCIBindByName(stmthp1, &bnd1p, errhp, (oratext*)":ENAME",
(sb4)strlen((char *)":ENAME"), (void *) ename, sizeof(ename),
SQLT_STR, (void *)&insname_ind, (ub2 *) 0, (ub2 *) 0,
(ub4) 0, (ub4 *)0, OCI_DEFAULT);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *) &ename_col_len,
(ub4) 0, (ub4)OCI_ATTR_MAXDATA_SIZE, errhp);
...
/* Retrieving Unicode data */
OCIDefineByPos (stmthp2, &dfn1p, errhp, (ub4)1, (void *)ename,
(sb4)sizeof(ename), SQLT_STR, (void *)0, (ub2 *)0, (ub2*)0,
(ub4)OCI_DEFAULT);
...

Binding and Defining SQL NCHAR Datatypes in OCI
Oracle recommends that you access SQL NCHAR datatypes using UTF-16 binding or
defining when using OCI. Beginning with Oracle9i, SQL NCHAR datatypes are Unicode
datatypes with an encoding of either UTF8 or AL16UTF16. To access data in SQL
NCHAR datatypes, set the OCI_ATTR_CHARSET_FORM attribute to SQLCS_NCHAR
between binding or defining and execution so that it performs an appropriate data
conversion without data loss. The length of data in SQL NCHAR datatypes is always in
the number of Unicode code units.
The following program is a typical example of inserting and fetching data against an
NCHAR data column:
...
ub2 csid = OCI_UTF16ID;
ub1 cform = SQLCS_NCHAR;
utext ename[100]; /* enough buffer for ENAME */
...
/* Inserting Unicode data */

Programming with Unicode 7-15

OCI Programming with Unicode

OCIBindByName(stmthp1, &bnd1p, errhp, (oratext*)":ENAME",
(sb4)strlen((char *)":ENAME"), (void *) ename,
sizeof(ename), SQLT_STR, (void *)&insname_ind, (ub2 *) 0,
(ub2 *) 0, (ub4) 0, (ub4 *)0, OCI_DEFAULT);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *) &cform, (ub4) 0,
(ub4)OCI_ATTR_CHARSET_FORM, errhp);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *) &csid, (ub4) 0,
(ub4)OCI_ATTR_CHARSET_ID, errhp);
OCIAttrSet((void *) bnd1p, (ub4) OCI_HTYPE_BIND, (void *) &ename_col_len,
(ub4) 0, (ub4)OCI_ATTR_MAXDATA_SIZE, errhp);
...
/* Retrieving Unicode data */
OCIDefineByPos (stmthp2, &dfn1p, errhp, (ub4)1, (void *)ename,
(sb4)sizeof(ename), SQLT_STR, (void *)0, (ub2 *)0, (ub2*)0,
(ub4)OCI_DEFAULT);
OCIAttrSet((void *) dfn1p, (ub4) OCI_HTYPE_DEFINE, (void *) &csid, (ub4) 0,
(ub4)OCI_ATTR_CHARSET_ID, errhp);
OCIAttrSet((void *) dfn1p, (ub4) OCI_HTYPE_DEFINE, (void *) &cform, (ub4) 0,
(ub4)OCI_ATTR_CHARSET_FORM, errhp);
...

Handling SQL NCHAR String Literals in OCI
By default, the NCHAR literal replacement is not performed in OCI. (Refer to "NCHAR
String Literal Replacement" on page 7-9.)
You can switch it on by setting the environment variable ORA_NCHAR_LITERAL_
REPLACE to TRUE. You can also achieve this behavior programmatically by using the
OCI_NCHAR_LITERAL_REPLACE_ON and OCI_NCHAR_LITERAL_REPLACE_OFF
modes in OCIEnvCreate() and OCIEnvNlsCreate(). So, for example,
OCIEnvCreate(OCI_NCHAR_LITERAL_REPLACE_ON) turns on NCHAR literal
replacement, while OCIEnvCreate(OCI_NCHAR_LITERAL_REPLACE_OFF) turns it
off.
As an example, consider the following statement:
int main(argc, argv)
{
OCIEnv *envhp;
if (OCIEnvCreate((OCIEnv **) &envhp,
(ub4)OCI_THREADED|OCI_NCHAR_LITERAL_REPLACE_ON,
(dvoid *)0, (dvoid * (*)(dvoid *, size_t)) 0,
(dvoid * (*)(dvoid *, dvoid *, size_t))0,
(void (*)(dvoid *, dvoid *)) 0,
(size_t) 0, (dvoid **) 0))
{
printf("FAILED: OCIEnvCreate()\n";
return 1;
}
...
}

Note that, when the NCHAR literal replacement is turned on, OCIStmtPrepare and
OCIStmtPrepare2 will transform N' literals with U' literals in the SQL text and
store the resulting SQL text in the statement handle. Thus, if the application uses OCI_
ATTR_STATEMENT to retrieve the SQL text from the OCI statement handle, the SQL
text will return U' instead of N' as specified in the original text.
See the Oracle Database SQL Reference for information regarding environment variables.

7-16 Oracle Database Globalization Support Guide

Pro*C/C++ Programming with Unicode

Binding and Defining CLOB and NCLOB Unicode Data in OCI
In order to write (bind) and read (define) UTF-16 data for CLOB or NCLOB columns, the
UTF-16 character set ID must be specified as OCILobWrite() and OCILobRead().
When you write UTF-16 data into a CLOB column, call OCILobWrite() as follows:
...
ub2 csid = OCI_UTF16ID;
err = OCILobWrite (ctx->svchp, ctx->errhp, lobp, &amtp, offset, (void *) buf,
(ub4) BUFSIZE, OCI_ONE_PIECE, (void *)0,
(sb4 (*)()) 0, (ub2) csid, (ub1) SQLCS_IMPLICIT);

The amtp parameter is the data length in number of Unicode code units. The offset
parameter indicates the offset of data from the beginning of the data column. The
csid parameter must be set for UTF-16 data.
To read UTF-16 data from CLOB columns, call OCILobRead() as follows:
...
ub2 csid = OCI_UTF16ID;
err = OCILobRead(ctx->svchp, ctx->errhp, lobp, &amtp, offset, (void *) buf,
(ub4)BUFSIZE , (void *) 0, (sb4 (*)()) 0, (ub2)csid,
(ub1) SQLCS_IMPLICIT);

The data length is always represented in the number of Unicode code units. Note one
Unicode supplementary character is counted as two code units, because the encoding
is UTF-16. After binding or defining a LOB column, you can measure the data length
stored in the LOB column using OCILobGetLength(). The returning value is the data
length in the number of code units if you bind or define as UTF-16.
err = OCILobGetLength(ctx->svchp, ctx->errhp, lobp, &lenp);

If you are using an NCLOB, then you must set OCI_ATTR_CHARSET_FORM to SQLCS_
NCHAR.

Pro*C/C++ Programming with Unicode
Pro*C/C++ provides the following ways to insert or retrieve Unicode data into or
from the database:
■

■

Using the VARCHAR Pro*C/C++ datatype or the native C/C++ text datatype, a
program can access Unicode data stored in SQL CHAR datatypes of a UTF8 or
AL32UTF8 database. Alternatively, a program could use the C/C++ native text
type.
Using the UVARCHAR Pro*C/C++ datatype or the native C/C++ utext datatype, a
program can access Unicode data stored in NCHAR datatypes of a database.
Using the NVARCHAR Pro*C/C++ datatype, a program can access Unicode data
stored in NCHAR datatypes. The difference between UVARCHAR and NVARCHAR in a
Pro*C/C++ program is that the data for the UVARCHAR datatype is stored in a
utext buffer while the data for the NVARCHAR datatype is stored in a text
datatype.

Pro*C/C++ does not use the Unicode OCI API for SQL text. As a result, embedded
SQL text must be encoded in the character set specified in the NLS_LANG environment
variable.
This section contains the following topics:
■

Pro*C/C++ Data Conversion in Unicode

Programming with Unicode 7-17

Pro*C/C++ Programming with Unicode

■

Using the VARCHAR Datatype in Pro*C/C++

■

Using the NVARCHAR Datatype in Pro*C/C++

■

Using the UVARCHAR Datatype in Pro*C/C++

Pro*C/C++ Data Conversion in Unicode
Data conversion occurs in the OCI layer, but it is the Pro*C/C++ preprocessor that
instructs OCI which conversion path should be taken based on the datatypes used in a
Pro*C/C++ program. Table 7–4 illustrates the conversion paths:
Table 7–4

Pro*C/C++ Bind and Define Data Conversion

Pro*C/C++ Datatype

SQL Datatype

Conversion Path

VARCHAR or text

CHAR

NLS_LANG character set to and from the database character
set happens in OCI

VARCHAR or text

NCHAR

NLS_LANG character set to and from database character set
happens in OCI
Database character set to and from national character set
happens in database server

NVARCHAR

NCHAR

NLS_LANG character set to and from national character set
happens in OCI

NVARCHAR

CHAR

NLS_LANG character set to and from national character set
happens in OCI
National character set to and from database character set in
database server

UVARCHAR or utext

NCHAR

UTF-16 to and from the national character set happens in
OCI

UVARCHAR or utext

CHAR

UTF-16 to and from national character set happens in OCI
National character set to database character set happens in
database server

Using the VARCHAR Datatype in Pro*C/C++
The Pro*C/C++ VARCHAR datatype is preprocessed to a struct with a length field
and text buffer field. The following example uses the C/C++ text native datatype
and the VARCHAR Pro*C/C++ datatypes to bind and define table columns.
#include
main()
{
...
/* Change to STRING datatype:
*/
EXEC ORACLE OPTION (CHAR_MAP=STRING) ;
text ename[20] ;
/* unsigned short type */
varchar address[50] ;
/* Pro*C/C++ varchar type */
EXEC SQL SELECT ename, address INTO :ename, :address FROM emp;
/* ename is NULL-terminated */
printf(L"ENAME = %s, ADDRESS = %.*s\n", ename, address.len, address.arr);
...
}

When you use the VARCHAR datatype or native text datatype in a Pro*C/C++
program, the preprocessor assumes that the program intends to access columns of SQL
CHAR datatypes instead of SQL NCHAR datatypes in the database. The preprocessor
7-18 Oracle Database Globalization Support Guide

Pro*C/C++ Programming with Unicode

generates C/C++ code to reflect this fact by doing a bind or define using the SQLCS_
IMPLICIT value for the OCI_ATTR_CHARSET_FORM attribute. As a result, if a bind or
define variable is bound to a column of SQL NCHAR datatypes in the database, then
implicit conversion occurs in the database server to convert the data from the database
character set to the national database character set and vice versa. During the
conversion, data loss occurs when the database character set is a smaller set than the
national character set.

Using the NVARCHAR Datatype in Pro*C/C++
The Pro*C/C++ NVARCHAR datatype is similar to the Pro*C/C++ VARCHAR datatype.
It should be used to access SQL NCHAR datatypes in the database. It tells Pro*C/C++
preprocessor to bind or define a text buffer to the column of SQL NCHAR datatypes.
The preprocessor specifies the SQLCS_NCHAR value for the OCI_ATTR_CHARSET_
FORM attribute of the bind or define variable. As a result, no implicit conversion occurs
in the database.
If the NVARCHAR buffer is bound against columns of SQL CHAR datatypes, then the
data in the NVARCHAR buffer (encoded in the NLS_LANG character set) is converted to
or from the national character set in OCI, and the data is then converted to the
database character set in the database server. Data can be lost when the NLS_LANG
character set is a larger set than the database character set.

Using the UVARCHAR Datatype in Pro*C/C++
The UVARCHAR datatype is preprocessed to a struct with a length field and utext
buffer field. The following example code contains two host variables, ename and
address. The ename host variable is declared as a utext buffer containing 20
Unicode characters. The address host variable is declared as a uvarchar buffer
containing 50 Unicode characters. The len and arr fields are accessible as fields of a
struct.
#include
#include
main()
{
...
/* Change to STRING datatype:
*/
EXEC ORACLE OPTION (CHAR_MAP=STRING) ;
utext ename[20] ;
/* unsigned short type */
uvarchar address[50] ;
/* Pro*C/C++ uvarchar type */
EXEC SQL SELECT ename, address INTO :ename, :address FROM emp;
/* ename is NULL-terminated */
wprintf(L"ENAME = %s, ADDRESS = %.*s\n", ename, address.len,
address.arr);
...
}

When you use the UVARCHAR datatype or native utext datatype in Pro*C/C++
programs, the preprocessor assumes that the program intends to access SQL NCHAR
datatypes. The preprocessor generates C/C++ code by binding or defining using the
SQLCS_NCHAR value for OCI_ATTR_CHARSET_FORM attribute. As a result, if a bind or
define variable is bound to a column of a SQL NCHAR datatype, then an implicit
conversion of the data from the national character set occurs in the database server.
However, there is no data lost in this scenario because the national character set is
always a larger set than the database character set.
Programming with Unicode 7-19

JDBC Programming with Unicode

JDBC Programming with Unicode
Oracle provides the following JDBC drivers for Java programs to access character data
in an Oracle database:
■

The JDBC OCI driver

■

The JDBC thin driver

■

The JDBC server-side internal driver

■

The JDBC server-side thin driver

Java programs can insert or retrieve character data to and from columns of SQL CHAR
and NCHAR datatypes. Specifically, JDBC enables Java programs to bind or define Java
strings to SQL CHAR and NCHAR datatypes. Because Java's string datatype is UTF-16
encoded, data retrieved from or inserted into the database must be converted from
UTF-16 to the database character set or the national character set and vice versa. JDBC
also enables you to specify the PL/SQL and SQL statements in Java strings so that any
non-ASCII schema object names and string literals can be used.
At database connection time, JDBC sets the server NLS_LANGUAGE and NLS_
TERRITORY parameters to correspond to the locale of the Java VM that runs the JDBC
driver. This operation ensures that the server and the Java client communicate in the
same language. As a result, Oracle error messages returned from the server are in the
same language as the client locale.
This section contains the following topics:
■

Binding and Defining Java Strings to SQL CHAR Datatypes

■

Binding and Defining Java Strings to SQL NCHAR Datatypes

■

Using the SQL NCHAR Datatypes Without Changing the Code

■

Using SQL NCHAR String Literals in JDBC

■

Data Conversion in JDBC

■

Using oracle.sql.CHAR in Oracle Object Types

■

Restrictions on Accessing SQL CHAR Data with JDBC

Binding and Defining Java Strings to SQL CHAR Datatypes
Oracle JDBC drivers allow you to access SQL CHAR datatypes in the database using
Java string bind or define variables. The following code illustrates how to bind a Java
string to a CHAR column.
int employee_id = 12345;
String last_name = "Joe";
PreparedStatement pstmt = conn.prepareStatement("INSERT INTO" +
"employees (last_name, employee_id) VALUES (?, ?)");
pstmt.setString(1, last_name);
pstmt.setInt(2, employee_id);
pstmt.execute();
/* execute to insert into first row */
employee_id += 1;
/* next employee number */
last_name = "\uFF2A\uFF4F\uFF45";
/* Unicode characters in name */
pstmt.setString(1, last_name);
pstmt.setInt(2, employee_id);
pstmt.execute();
/* execute to insert into second row */

You can define the target SQL columns by specifying their datatypes and lengths.
When you define a SQL CHAR column with the datatype and the length, JDBC uses

7-20 Oracle Database Globalization Support Guide

JDBC Programming with Unicode

this information to optimize the performance of fetching SQL CHAR data from the
column. The following is an example of defining a SQL CHAR column.
OraclePreparedStatement pstmt = (OraclePreparedStatement)
conn.prepareStatement("SELECT ename, empno from emp");
pstmt.defineColumnType(1,Types.VARCHAR, 3);
pstmt.defineColumnType(2,Types.INTEGER);
ResultSet rest = pstmt.executeQuery();
String name = rset.getString(1);
int id = reset.getInt(2);

You need to cast PreparedStatement to OraclePreparedStatement to call
defineColumnType(). The second parameter of defineColumnType() is the
datatype of the target SQL column. The third parameter is the length in number of
characters.

Binding and Defining Java Strings to SQL NCHAR Datatypes
For binding or defining Java string variables to SQL NCHAR datatypes, Oracle provides
an extended PreparedStatement which has the setFormOfUse() method through
which you can explicitly specify the target column of a bind variable to be a SQL
NCHAR datatype. The following code illustrates how to bind a Java string to an NCHAR
column.
int employee_id = 12345;
String last_name = "Joe"
oracle.jdbc.OraclePreparedStatement pstmt =
(oracle.jdbc.OraclePreparedStatement)
conn.prepareStatement("INSERT INTO employees (last_name, employee_id)
VALUES
(?, ?)");
pstmt.setFormOfUse(1, oracle.jdbc.OraclePreparedStatement.FORM_NCHAR);
pstmt.setString(1, last_name);
pstmt.setInt(2, employee_id);
pstmt.execute();
/* execute to insert into first row */
employee_id += 1;
/* next employee number */
last_name = "\uFF2A\uFF4F\uFF45";
/* Unicode characters in name */
pstmt.setString(1, last_name);
pstmt.setInt(2, employee_id);
pstmt.execute();
/* execute to insert into second row */

You can define the target SQL NCHAR columns by specifying their datatypes, forms of
use, and lengths. JDBC uses this information to optimize the performance of fetching
SQL NCHAR data from these columns. The following is an example of defining a SQL
NCHAR column.
OraclePreparedStatement pstmt = (OraclePreparedStatement)
conn.prepareStatement("SELECT ename, empno from emp");
pstmt.defineColumnType(1,Types.VARCHAR, 3,
OraclePreparedStatement.FORM_NCHAR);
pstmt.defineColumnType(2,Types.INTEGER);
ResultSet rest = pstmt.executeQuery();
String name = rset.getString(1);
int id = reset.getInt(2);

To define a SQL NCHAR column, you need to specify the datatype that is equivalent to
a SQL CHAR column in the first argument, the length in number of characters in the
second argument, and the form of use in the fourth argument of
defineColumnType().

Programming with Unicode 7-21

JDBC Programming with Unicode

You can bind or define a Java string against an NCHAR column without explicitly
specifying the form of use argument. This implies the following:
■

■

If you do not specify the argument in the setString() method, then JDBC
assumes that the bind or define variable is for the SQL CHAR column. As a result, it
tries to convert them to the database character set. When the data gets to the
database, the database implicitly converts the data in the database character set to
the national character set. During this conversion, data can be lost when the
database character set is a subset of the national character set. Because the national
character set is either UTF8 or AL16UTF16, data loss would happen if the database
character set is not UTF8 or AL32UTF8.
Because implicit conversion from SQL CHAR to SQL NCHAR datatypes happens in
the database, database performance is degraded.

In addition, if you bind or define a Java string for a column of SQL CHAR datatypes but
specify the form of use argument, then performance of the database is degraded.
However, data should not be lost because the national character set is always a larger
set than the database character set.

Using the SQL NCHAR Datatypes Without Changing the Code
A Java system property has been introduced in the Oracle JDBC drivers for customers
to tell whether the form of use argument should be specified by default in a Java
application. This property has the following purposes:
■

■

Existing applications accessing the SQL CHAR datatypes can be migrated to
support the SQL NCHAR datatypes for worldwide deployment without changing a
line of code.
Applications do not need to call the setFormOfUse() method when binding and
defining a SQL NCHAR column. The application code can be made neutral and
independent of the datatypes being used in the backend database. With this
property set, applications can be easily switched from using SQL CHAR or SQL
NCHAR.

The Java system property is specified in the command line that invokes the Java
application. The syntax of specifying this flag is as follows:
java -Doracle.jdbc.defaultNChar=true

With this property specified, the Oracle JDBC drivers assume the presence of the form
of use argument for all bind and define operations in the application.
If you have a database schema that consists of both the SQL CHAR and SQL NCHAR
columns, then using this flag may have some performance impact when accessing the
SQL CHAR columns because of implicit conversion done in the database server.
See Also: "Data Conversion in JDBC" on page 7-23 for more
information about the performance impact of implicit conversion

Using SQL NCHAR String Literals in JDBC
When using NCHAR string literals in JDBC, there is a potential for data loss because
characters are converted to the database character set before processing. See NCHAR
String Literal Replacement on page 7-9 for more details.
The desired behavior for preserving the NCHAR string literals can be achieved by
enabling the property set oracle.jdbc.convertNcharLiterals. If the value is
true, then this option is enabled; otherwise, it is disabled. The default setting is false. It

7-22 Oracle Database Globalization Support Guide

JDBC Programming with Unicode

can be enabled in two ways: a) as a Java system property or b) as a connection
property. Once enabled, conversion is performed on all SQL in the VM (system
property) or in the connection (connection property). For example, the property can be
set as a Java system property as follows:
java -Doracle.jdbc.convertNcharLiterals="true" ...

Alternatively, you can set this as a connection property as follows:
Properties props = new Properties();
...
props.setProperty("oracle.jdbc.convertNcharLiterals", "true");
Connection conn = DriverManager.getConnection(url, props);

If you set this as a connection property, it overrides a system property setting.

Data Conversion in JDBC
Because Java strings are always encoded in UTF-16, JDBC drivers transparently
convert data from the database character set to UTF-16 or the national character set.
The conversion paths taken are different for the JDBC drivers:
■

Data Conversion for the OCI Driver

■

Data Conversion for Thin Drivers

■

Data Conversion for the Server-Side Internal Driver

Data Conversion for the OCI Driver
For the OCI driver, the SQL statements are always converted to the database character
set by the driver before it is sent to the database for processing. When the database
character set is neither US7ASCII nor WE8ISO8859P1, the driver converts the SQL
statements to UTF-8 first in Java and then to the database character set in C.
Otherwise, it converts the SQL statements directly to the database character set. For
Java string bind or define variables, Table 7–5 summarizes the conversion paths taken
for different scenarios.
Table 7–5

OCI Driver Conversion Path

Form of Use

SQL Datatype

Conversion Path

Const.CHAR
(Default)

CHAR

Java string to and from database character set happens in the JDBC driver.

Const.CHAR
(Default)

NCHAR

Java string to and from database character set happens in the JDBC driver.

Const.NCHAR

NCHAR

Java string to and from national character set happens in the JDBC driver.

Const.NCHAR

CHAR

Java string to and from national character set happens in the JDBC driver.

Data in the database character set to and from national character set
happens in the database server.

Data in national character set to and from database character set happens
in the database server.

Data Conversion for Thin Drivers
SQL statements are always converted to either the database character set or to UTF-8
by the driver before they are sent to the database for processing. When the database
character set is either US7ASCII or WE8ISO8859P1, the driver converts the SQL
statement to the database character set. Otherwise, the driver converts the SQL
statement to UTF-8 and notifies the database that a SQL statement requires further

Programming with Unicode 7-23

JDBC Programming with Unicode

conversion before being processed. The database, in turn, converts the SQL statements
from UTF-8 to the database character set. The database, in turn, converts the SQL
statement to the database character set. For Java string bind and define variables, the
conversion paths shown in Table 7–6 are taken for the thin driver.
Table 7–6

Thin Driver Conversion Path
Database
Character Set

Conversion Path

CHAR

US7ASCII or
WE8ISO8859P1

Java string to and from the database character set
happens in the thin driver.

NCHAR

US7ASCII or
WE8ISO8859P1

Java string to and from the database character set
happens in the thin driver.

Form of Use

SQL Datatype

Const.CHAR
(Default)
Const.CHAR
(Default)

Data in the database character set to and from the
national character set happens in the database server.
Const.CHAR
(Default)

CHAR

non-ASCII and
non-WE8ISO8859P1

Java string to and from UTF-8 happens in the thin
driver.
Data in UTF-8 to and from the database character set
happens in the database server.

Const.CHAR
(Default)

NCHAR

non-ASCII and
non-WE8ISO8859P1

Java string to and from UTF-8 happens in the thin
driver.
Data in UTF-8 to and from national character set
happens in the database server.

Const.NCHAR

CHAR

Java string to and from the national character set
happens in the thin driver.
Data in the national character set to and from the
database character set happens in the database server.

Const.NCHAR

NCHAR

Java string to and from the national character set
happens in the thin driver.

Data Conversion for the Server-Side Internal Driver
All data conversion occurs in the database server because the server-side internal
driver works inside the database.

Using oracle.sql.CHAR in Oracle Object Types
JDBC drivers support Oracle object types. Oracle objects are always sent from database
to client as an object represented in the database character set or national character set.
That means the data conversion path in "Data Conversion in JDBC" on page 7-23 does
not apply to Oracle object access. Instead, the oracle.sql.CHAR class is used for
passing SQL CHAR and SQL NCHAR data of an object type from the database to the
client.
This section includes the following topics:
■

oracle.sql.CHAR

■

Accessing SQL CHAR and NCHAR Attributes with oracle.sql.CHAR

oracle.sql.CHAR
The oracle.sql.CHAR class has a special functionality for conversion of character
data. The Oracle character set is a key attribute of the oracle.sql.CHAR class. The
Oracle character set is always passed in when an oracle.sql.CHAR object is

7-24 Oracle Database Globalization Support Guide

JDBC Programming with Unicode

constructed. Without a known character set, the bytes of data in the
oracle.sql.CHAR object are meaningless.
The oracle.sql.CHAR class provides the following methods for converting
character data to strings:
■

getString()
Converts the sequence of characters represented by the oracle.sql.CHAR object
to a string, returning a Java string object. If the character set is not recognized, then
getString() returns a SQLException.

■

toString()
Identical to getString(), except that if the character set is not recognized, then
toString() returns a hexadecimal representation of the oracle.sql.CHAR
data and does not returns a SQLException.

■

getStringWithReplacement()
Identical to getString(), except that a default replacement character replaces
characters that have no Unicode representation in the character set of this
oracle.sql.CHAR object. This default character varies among character sets, but
it is often a question mark.

You may want to construct an oracle.sql.CHAR object yourself (to pass into a
prepared statement, for example). When you construct an oracle.sql.CHAR object,
you must provide character set information to the oracle.sql.CHAR object by using
an instance of the oracle.sql.CharacterSet class. Each instance of the
oracle.sql.CharacterSet class represents one of the character sets that Oracle
supports.
Complete the following tasks to construct an oracle.sql.CHAR object:
1.

Create a CharacterSet instance by calling the static CharacterSet.make()
method. This method creates the character set class. It requires as input a valid
Oracle character set (OracleId). For example:
int OracleId = CharacterSet.JA16SJIS_CHARSET; // this is character set 832
...
CharacterSet mycharset = CharacterSet.make(OracleId);

Each character set that Oracle supports has a unique predefined OracleId. The
OracleId can always be referenced as a character set specified as Oracle_
character_set_name_CHARSET where Oracle_character_set_name is the
Oracle character set.
2.

Construct an oracle.sql.CHAR object. Pass to the constructor a string (or the
bytes that represent the string) and the CharacterSet object that indicates how
to interpret the bytes based on the character set. For example:
String mystring = "teststring";
...
oracle.sql.CHAR mychar = new oracle.sql.CHAR(teststring, mycharset);

The oracle.sql.CHAR class has multiple constructors: they can take a string, a
byte array, or an object as input along with the CharacterSet object. In the case
of a string, the string is converted to the character set indicated by the
CharacterSet object before being placed into the oracle.sql.CHAR object.
The server (database) and the client (or application running on the client) can use
different character sets. When you use the methods of this class to transfer data

Programming with Unicode 7-25

JDBC Programming with Unicode

between the server and the client, the JDBC drivers must convert the data between the
server character set and the client character set.

Accessing SQL CHAR and NCHAR Attributes with oracle.sql.CHAR
The following is an example of an object type created using SQL:
CREATE TYPE person_type AS OBJECT (
name VARCHAR2(30), address NVARCHAR2(256), age NUMBER);
CREATE TABLE employees (id NUMBER, person PERSON_TYPE);

The Java class corresponding to this object type can be constructed as follows:
public class person implement SqlData
{
oracle.sql.CHAR name;
oracle.sql.CHAR address;
oracle.sql.NUMBER age;
// SqlData interfaces
getSqlType() {...}
writeSql(SqlOutput stream) {...}
readSql(SqlInput stream, String sqltype) {...}
}

The oracle.sql.CHAR class is used here to map to the NAME attributes of the Oracle
object type, which is of VARCHAR2 datatype. JDBC populates this class with the byte
representation of the VARCHAR2 data in the database and the CharacterSet object
corresponding to the database character set. The following code retrieves a person
object from the employees table:
TypeMap map = ((OracleConnection)conn).getTypeMap();
map.put("PERSON_TYPE", Class.forName("person"));
conn.setTypeMap(map);
.
.
.
.
.
.
ResultSet rs = stmt.executeQuery(
"SELECT PERSON FROM EMPLOYEES");
rs.next();
person p = (person) rs.getObject(1);
oracle.sql.CHAR sql_name = p.name;
oracle.sql.CHAR sql_address=p.address;
String java_name = sql_name.getString();
String java_address = sql_address.getString();

The getString() method of the oracle.sql.CHAR class converts the byte array
from the database character set or national character set to UTF-16 by calling Oracle's
Java data conversion classes and returning a Java string. For the rs.getObject(1)
call to work, the SqlData interface has to be implemented in the class person, and
the Typemap map has to be set up to indicate the mapping of the object type PERSON_
TYPE to the Java class.

Restrictions on Accessing SQL CHAR Data with JDBC
This section contains the following topic:
■

Character Integrity Issues in a Multibyte Database Environment

Character Integrity Issues in a Multibyte Database Environment
Oracle JDBC drivers perform character set conversions as appropriate when character
data is inserted into or retrieved from the database. The drivers convert Unicode
7-26 Oracle Database Globalization Support Guide

ODBC and OLE DB Programming with Unicode

characters used by Java clients to Oracle database character set characters, and vice
versa. Character data that makes a round trip from the Java Unicode character set to
the database character set and back to Java can suffer some loss of information. This
happens when multiple Unicode characters are mapped to a single character in the
database character set. An example is the Unicode full-width tilde character (0xFF5E)
and its mapping to Oracle's JA16SJIS character set. The round-trip conversion for this
Unicode character results in the Unicode character 0x301C, which is a wave dash (a
character commonly used in Japan to indicate range), not a tilde.
Figure 7–2 shows the round-trip conversion of the tilde character.
Figure 7–2 Character Integrity

Java Unicode

0x301C

0xFF5E

Oracle database
Character Set
(JA16SJIS)

..
.
..
.
..
.

..
.
..
.

Java Unicode

0x8160

..
.
..
.
..
.

0x301C

0xFF5E

This issue is not a bug in Oracle's JDBC. It is an unfortunate side effect of the
ambiguity in character mapping specifications on different operating systems.
Fortunately, this problem affects only a small number of characters in a small number
of Oracle character sets such as JA16SJIS, JA16EUC, ZHT16BIG5, and KO16KS5601.
The workaround is to avoid making a full round-trip with these characters.

ODBC and OLE DB Programming with Unicode
You should use the Oracle ODBC driver or Oracle Provider for OLE DB to access the
Oracle server when using a Windows platform. This section describes how these
drivers support Unicode. It includes the following topics:
■

Unicode-Enabled Drivers in ODBC and OLE DB

■

OCI Dependency in Unicode

■

ODBC and OLE DB Code Conversion in Unicode

■

ODBC Unicode Datatypes

■

OLE DB Unicode Datatypes

■

ADO Access

Unicode-Enabled Drivers in ODBC and OLE DB
Oracle's ODBC driver and Oracle Provider for OLE DB can handle Unicode data
properly without data loss. For example, you can run a Unicode ODBC application
containing Japanese data on English Windows if you install Japanese fonts and an
input method editor for entering Japanese characters.

Programming with Unicode 7-27

ODBC and OLE DB Programming with Unicode

Oracle provides ODBC and OLE DB products for Windows platforms only. For Unix
platforms, contact your vendor.

OCI Dependency in Unicode
OCI Unicode binding and defining features are used by the ODBC and OLE DB
drivers to handle Unicode data. OCI Unicode data binding and defining features are
independent from NLS_LANG. This means Unicode data is handled properly,
irrespective of the NLS_LANG setting on the platform.
See Also:

"OCI Programming with Unicode" on page 7-10

ODBC and OLE DB Code Conversion in Unicode
In general, no redundant data conversion occurs unless you specify a different client
datatype from that of the server. If you bind Unicode buffer SQL_C_WCHAR with a
Unicode data column like NCHAR, for example, then ODBC and OLE DB drivers
bypass it between the application and OCI layer.
If you do not specify datatypes before fetching, but call SQLGetData with the client
datatypes instead, then the conversions in Table 7–7 occur.
Table 7–7

ODBC Implicit Binding Code Conversions

Datatypes of the
Datatypes of ODBC Target Column in
Client Buffer
the Database
SQL_C_WCHAR

SQL_C_CHAR

CHAR,
VARCHAR2,
CLOB

Fetch Conversions

Comments

If the database character set is a subset
of the NLS_LANG character set, then the
conversions occur in the following
order:

No unexpected data loss

■

Database character set

■

NLS_LANG

■

UTF-16 in OCI

■

UTF-16 in ODBC

If database character set is a subset of
NLS_LANG character set:
Database character set to NLS_LANG in
OCI
If database character set is NOT a subset
of NLS_LANG character set:

May degrade performance
if database character set is
a subset of the NLS_LANG
character set

No unexpected data loss
May degrade performance
if database character set is
not a subset of NLS_LANG
character set

Database character set, UTF-16, to NLS_
LANG character set in OCI and ODBC

You must specify the datatype for inserting and updating operations.
The datatype of the ODBC client buffer is given when you call SQLGetData but not
immediately. Hence, SQLFetch does not have the information.
Because the ODBC driver guarantees data integrity, if you perform implicit bindings,
then redundant conversion may result in performance degradation. Your choice is the
trade-off between performance with explicit binding or usability with implicit binding.

7-28 Oracle Database Globalization Support Guide

ODBC and OLE DB Programming with Unicode

OLE DB Code Conversions
Unlike ODBC, OLE DB only enables you to perform implicit bindings for inserting,
updating, and fetching data. The conversion algorithm for determining the
intermediate character set is the same as the implicit binding cases of ODBC.
Table 7–8

OLE DB Implicit Bindings

Datatypes of OLE_
DB Client Buffer
DBTYPE_WCHAR

Datatypes of the
Target Column in the In-Binding and Out-Binding
Database
Conversions
CHAR,
VARCHAR2,
CLOB

If database character set is a
subset of the NLS_LANG character
set:

Comments
No unexpected data loss

May degrade performance if
database character set is a
Database character set to and from subset of NLS_LANG character
set
NLS_LANG character set in OCI.
NLS_LANG character set to UTF-16
in OLE DB
If database character set is NOT a
subset of NLS_LANG character set:
Database character set to and from
UTF-16 in OCI

DBTYPE_CHAR

CHAR,
VARCHAR2,
CLOB

If database character set is a
subset of the NLS_LANG character
set:

No unexpected data loss

May degrade performance if
database character set is not a
Database character set to and from subset of NLS_LANG character
NLS_LANG in OCI
set
If database character set is not a
subset of NLS_LANG character set:
Database character set to and from
UTF-16 in OCI. UTF-16 to NLS_
LANG character set in OLE DB

ODBC Unicode Datatypes
In ODBC Unicode applications, use SQLWCHAR to store Unicode data. All standard
Windows Unicode functions can be used for SQLWCHAR data manipulations. For
example, wcslen counts the number of characters of SQLWCHAR data:
SQLWCHAR sqlStmt[] = L"select ename from emp";
len = wcslen(sqlStmt);

Microsoft's ODBC 3.5 specification defines three Unicode datatype identifiers for the
SQL_C_WCHAR, SQL_C_WVARCHAR, and SQL_WLONGVARCHAR clients; and three
Unicode datatype identifiers for servers SQL_WCHAR, SQL_WVARCHAR, and SQL_
WLONGVARCHAR.
For binding operations, specify datatypes for both client and server using
SQLBindParameter. The following is an example of Unicode binding, where the
client buffer Name indicates that Unicode data (SQL_C_WCHAR) is bound to the first
bind variable associated with the Unicode column (SQL_WCHAR):
SQLBindParameter(StatementHandle, 1, SQL_PARAM_INPUT, SQL_C_WCHAR,
SQL_WCHAR, NameLen, 0, (SQLPOINTER)Name, 0, &Name);

Programming with Unicode 7-29

ODBC and OLE DB Programming with Unicode

Table 7–9 represents the datatype mappings of the ODBC Unicode datatypes for the
server against SQL NCHAR datatypes.
Table 7–9

Server ODBC Unicode Datatype Mapping

ODBC Datatype

Oracle Datatype

SQL_WCHAR

NCHAR

SQL_WVARCHAR

NVARCHAR2

SQL_WLONGVARCHAR

NCLOB

According to ODBC specifications, SQL_WCHAR, SQL_WVARCHAR, and SQL_
WLONGVARCHAR are treated as Unicode data, and are therefore measured in the
number of characters instead of the number of bytes.

OLE DB Unicode Datatypes
OLE DB offers the wchar_t, BSTR, and OLESTR datatypes for a Unicode C client. In
practice, wchar_t is the most common datatype and the others are for specific
purposes. The following example assigns a static SQL statement:
wchar_t *sqlStmt = OLESTR("SELECT ename FROM emp");

The OLESTR macro works exactly like an "L" modifier to indicate the Unicode string. If
you need to allocate Unicode data buffer dynamically using OLESTR, then use the
IMalloc allocator (for example, CoTaskMemAlloc). However, using OLESTR is not
the normal method for variable length data; use wchar_t* instead for generic string
types. BSTR is similar. It is a string with a length prefix in the memory location
preceding the string. Some functions and methods can accept only BSTR Unicode
datatypes. Therefore, BSTR Unicode string must be manipulated with special
functions like SysAllocString for allocation and SysFreeString for freeing
memory.
Unlike ODBC, OLE DB does not allow you to specify the server datatype explicitly.
When you set the client datatype, the OLE DB driver automatically performs data
conversion if necessary.
Table 7–10 illustrates OLE DB datatype mapping.
Table 7–10

OLE DB Datatype Mapping

OLE DB Datatype

Oracle Datatype

DBTYPE_WCHAR

NCHAR or NVARCHAR2

If DBTYPE_BSTR is specified, then it is assumed to be DBTYPE_WCHAR because both
are Unicode strings.

ADO Access
ADO is a high-level API to access database with the OLE DB and ODBC drivers. Most
database application developers use the ADO interface on Windows because it is
easily accessible from Visual Basic, the primary scripting language for Active Server
Pages (ASP) for the Internet Information Server (IIS). To OLE DB and ODBC drivers,
ADO is simply an OLE DB consumer or ODBC application. ADO assumes that OLE
DB and ODBC drivers are Unicode-aware components; hence, it always attempts to
manipulate Unicode data.

7-30 Oracle Database Globalization Support Guide

XML Programming with Unicode

XML Programming with Unicode
XML support of Unicode is essential for software development for global markets so
that text information can be exchanged in any language. Unicode uniformly supports
almost every character and language, which makes it much easier to support multiple
languages within XML. To enable Unicode for XML within an Oracle database, the
character set of the database must be UTF-8. By enabling Unicode text handling in
your application, you acquire a basis for supporting any language. Every XML
document is Unicode text and potentially multilingual, unless it is guaranteed that
only a known subset of Unicode characters will appear on your documents. Thus
Oracle recommends that you enable Unicode for XML. Unicode support comes with
Java and many other modern programming environments.
This section includes the following topics:
■

Writing an XML File in Unicode with Java

■

Reading an XML File in Unicode with Java

■

Parsing an XML Stream in Unicode with Java

Writing an XML File in Unicode with Java
A common mistake in reading and writing XML files is using the Reader and Writer
classes for character input and output. Using Reader and Writer for XML files
should be avoided because it requires character set conversion based on the default
character encoding of the runtime environment.
For example, using FileWriter class is not safe because it converts the document to
the default character encoding. The output file can suffer from a parsing error or data
loss if the document contains characters that are not available in the default character
encoding.
UTF-8 is popular for XML documents, but UTF-8 is not usually the default file
encoding for Java. Thus using a Java class that assumes the default file encoding can
cause problems.
The following example shows how to avoid these problems:
import java.io.*;
import oracle.xml.parser.v2.*;
public class I18nSafeXMLFileWritingSample
{
public static void main(String[] args) throws Exception
{
// create a test document
XMLDocument
doc = new XMLDocument();
doc.setVersion( "1.0" );
doc.appendChild(doc.createComment( "This is a test empty document." ));
doc.appendChild(doc.createElement( "root" ));
// create a file
File

file = new File( "myfile.xml" );

// create a binary output stream to write to the file just created
FileOutputStream
fos = new FileOutputStream( file );
// create a Writer that converts Java character stream to UTF-8 stream
OutputStreamWriter osw = new OutputStreamWriter( fos, "UTF8" );

Programming with Unicode 7-31

XML Programming with Unicode

// buffering for efficiency
Writer
w
= new BufferedWriter( osw );
// create a PrintWriter to adapt to the printing method
PrintWriter
out = new PrintWriter( w );
// print the document to the file through the connected objects
doc.print( out );
}
}

Reading an XML File in Unicode with Java
Do not read XML files as text input. When reading an XML document stored in a file
system, use the parser to automatically detect the character encoding of the document.
Avoid using a Reader class or specifying a character encoding on the input stream.
Given a binary input stream with no external encoding information, the parser
automatically figures out the character encoding based on the byte order mark and
encoding declaration of the XML document. Any well-formed document in any
supported encoding can be successfully parsed using the following sample code:
import java.io.*;
import oracle.xml.parser.v2.*;
public class I18nSafeXMLFileReadingSample
{
public static void main(String[] args) throws Exception
{
// create an instance of the xml file
File
file = new File( "myfile.xml" );
// create a binary input stream
FileInputStream
fis = new FileInputStream( file );
// buffering for efficiency
BufferedInputStream in = new BufferedInputStream( fis );
// get an instance of the parser
DOMParser parser = new DOMParser();
// parse the xml file
parser.parse( in );
}
}

Parsing an XML Stream in Unicode with Java
When the source of an XML document is not a file system, the encoding information is
usually available before reading the document. For example, if the input document is
provided in the form of a Java character stream or Reader, its encoding is evident and
no detection should take place. The parser can begin parsing a Reader in Unicode
without regard to the character encoding.
The following is an example of parsing a document with external encoding
information:
import
import
import
import

java.io.*;
java.net.*;
org.xml.sax.*;
oracle.xml.parser.v2.*;

7-32 Oracle Database Globalization Support Guide

XML Programming with Unicode

public class I18nSafeXMLStreamReadingSample
{
public static void main(String[] args) throws Exception
{
// create an instance of the xml file
URL url = new URL( "http://myhost/mydocument.xml" );
// create a connection to the xml document
URLConnection conn = url.openConnection();
// get an input stream
InputStream is = conn.getInputStream();
// buffering for efficiency
BufferedInputStream bis = new BufferedInputStream( is );
/* figure out the character encoding here
*/
/* a typical source of encoding information is the content-type header */
/* we assume it is found to be utf-8 in this example
*/
String charset = "utf-8";
// create an InputSource for UTF-8 stream
InputSource in = new InputSource( bis );
in.setEncoding( charset );
// get an instance of the parser
DOMParser parser = new DOMParser();
// parse the xml stream
parser.parse( in );
}
}

Programming with Unicode 7-33

XML Programming with Unicode

7-34 Oracle Database Globalization Support Guide

8
Oracle Globalization Development Kit
This chapter includes the following sections:
■

Overview of the Oracle Globalization Development Kit

■

Designing a Global Internet Application

■

Developing a Global Internet Application

■

Getting Started with the Globalization Development Kit

■

GDK Quick Start

■

GDK Application Framework for J2EE

■

GDK Java API

■

The GDK Application Configuration File

■

GDK for Java Supplied Packages and Classes

■

GDK for PL/SQL Supplied Packages

■

GDK Error Messages

Overview of the Oracle Globalization Development Kit
Designing and developing a globalized application can be a daunting task even for the
most experienced developers. This is usually caused by lack of knowledge and the
complexity of globalization concepts and APIs. Application developers who write
applications using Oracle Database need to understand the Globalization Support
architecture of the database, including the properties of the different character sets,
territories, languages and linguistic sort definitions. They also need to understand the
globalization functionality of their middle-tier programming environment, and find
out how it can interact and synchronize with the locale model of the database. Finally,
to develop a globalized Internet application, they need to design and write code that is
capable of simultaneously supporting multiple clients running on different operating
systems, with different character sets and locale requirements.
Oracle Globalization Development Kit (GDK) simplifies the development process and
reduces the cost of developing Internet applications that will be used to support a
global environment. The GDK includes comprehensive programming APIs for both
Java and PL/SQL, code samples, and documentation that address many of the design,
development, and deployment issues encountered while creating global applications.
The GDK mainly consists of two parts: GDK for Java and GDK for PL/SQL. GDK for
Java provides globalization support to Java applications. GDK for PL/SQL provides
globalization support to the PL/SQL programming environment. The features offered
in GDK for Java and GDK for PL/SQL are not identical.
Oracle Globalization Development Kit

8-1

Designing a Global Internet Application

Designing a Global Internet Application
There are two architectural models for deploying a global Web site or a global Internet
application, depending on your globalization and business requirements. Which
model to deploy affects how the Internet application is developed and how the
application server is configured in the middle-tier. The two models are:
■

Multiple instances of monolingual Internet applications
Internet applications that support only one locale in a single binary are classified
as monolingual applications. A locale refers to a national language and the region
in which the language is spoken. For example, the primary language of the United
States and Great Britain is English. However, the two territories have different
currencies and different conventions for date formats. Therefore, the United States
and Great Britain are considered to be two different locales.
This level of globalization support is suitable for customers who want to support
one locale for each instance of the application. Users need to have different entry
points to access the applications for different locales. This model is manageable
only if the number of supported locales is small.

■

Single instance of a multilingual application
Internet applications that support multiple locales simultaneously in a single
binary are classified as multilingual applications. This level of globalization
support is suitable for customers who want to support several locales in an
Internet application simultaneously. Users of different locale preferences use the
same entry point to access the application.
Developing an application using the monolingual model is very different from
developing an application using the multilingual model. The Globalization
Development Kit consists of libraries, which can assist in the development of
global applications using either architectural model.

The rest of this section includes the following topics:
■

Deploying a Monolingual Internet Application

■

Deploying a Multilingual Internet Application

Deploying a Monolingual Internet Application
Deploying a global Internet application with multiple instances of monolingual
Internet applications is shown in Figure 8–1.

8-2 Oracle Database Globalization Support Guide

Designing a Global Internet Application

Figure 8–1 Monolingual Internet Application Architecture
Browsers

Application Server

Customer
Database

Server A
ISO-8859-1

Monolingual
Application:
English Locale

WE8MSWIN1252

Application Server
Instance 1

English
Locale

Application Server
Instance 2

Shift-JIS

Monolingual
Application:
Japanese Locale

JAI6SJIS

Japanese
Locale

Oracle
Unicode
Database

Server B
ISO-8859-8

Hebrew
Locale

Monolingual
Application:
Hebrew Locale

IW8MSWIN1255

Application Server
Instance 3
HTTP
Oracle Net

Each application server is configured for the locale that it serves. This deployment
model assumes that one instance of an Internet application runs in the same locale as
the application in the middle tier.
The Internet applications access a back-end database in the native encoding used for
the locale. The following are advantages of deploying monolingual Internet
applications:
■

■

The support of the individual locales is separated into different servers so that
multiple locales can be supported independently in different locations and that the
workload can be distributed accordingly. For example, customers may want to
support Western European locales first and then support Asian locales such as
Japanese (Japan) later.
The complexity required to support multiple locales simultaneously is avoided.
The amount of code to write is significantly less for a monolingual Internet
application than for a multilingual Internet application.

The following are disadvantages of deploying monolingual Internet applications:
■

■

Extra effort is required to maintain and manage multiple servers for different
locales. Different configurations are required for different application servers.
The minimum number of application servers required depends on the number of
locales the application supports, regardless of whether the site traffic will reach the
capacity provided by the application servers.

Oracle Globalization Development Kit

8-3

Designing a Global Internet Application

■

Load balancing for application servers is limited to the group of application
servers for the same locale.
More QA resources, both human and machine, are required for multiple
configurations of application servers. Internet applications running on different
locales must be certified on the corresponding application server configuration.
It is not designed to support multilingual content. For example, a web page
containing Japanese and Arabic data cannot be easily supported in this model.

As more and more locales are supported, the disadvantages quickly outweigh the
advantages. With the limitation and the maintenance overhead of the monolingual
deployment model, this deployment architecture is suitable for applications that
support only one or two locales.

Deploying a Multilingual Internet Application
Multilingual Internet applications are deployed to the application servers with a single
application server configuration that works for all locales. Figure 8–2 shows the
architecture of a multilingual Internet application.
Figure 8–2 Multilingual Internet Application Architecture
Browsers

Customer
Database
ISO-8859-1

English
Locale
Shift-JIS
Server
Multilingual
Application with
Dynamic Locale
Switching

Japanese
Locale
UTF-8

Unicode

Oracle
Unicode
Database

Application Server
Instance

Hebrew
Locale

UTF-8
HTTP
Oracle Net
Thai
Locale

To support multiple locales in a single application instance, the application may need
to do the following:
■

Dynamically detect the locale of the users and adapt to the locale by constructing
HTML pages in the language and cultural conventions of the locale

8-4 Oracle Database Globalization Support Guide

Developing a Global Internet Application

■

Process character data in Unicode so that data in any language can be supported.
Character data can be entered by users or retrieved from back-end databases.
Dynamically determine the HTML page encoding (or character set) to be used for
HTML pages and convert content from Unicode to the page encoding and the
reverse.

The following are major advantages of deploying multilingual Internet application:
■

■

Using a single application server configuration for all application servers
simplifies the deployment configuration and hence reduces the cost of
maintenance.
Performance tuning and capacity planning do not depend on the number of
locales supported by the Web site.
Introducing additional locales is relatively easy. No extra machines are necessary
for the new locales.
Testing the application across different locales can be done in a single testing
environment.
This model can support multilingual content within the same instance of the
application. For example, a web page containing Japanese, Chinese, English and
Arabic data can be easily supported in this model.

The disadvantage of deploying multilingual Internet applications is that it requires
extra coding during application development to handle dynamic locale detection and
Unicode, which is costly when only one or two languages need to be supported.
Deploying multilingual Internet applications is more appropriate than deploying
monolingual applications when Web sites support multiple locales.

Developing a Global Internet Application
Building an Internet application that supports different locales requires good
development practices.
For multilingual Internet applications, the application itself must be aware of the user's
locale and be able to present locale-appropriate content to the user. Clients must be
able to communicate with the application server regardless of the client's locale. The
application server then communicates with the database server, exchanging data while
maintaining the preferences of the different locales and character set settings. One of
the main considerations when developing a multilingual Internet application is to be
able to dynamically detect, cache, and provide the appropriate contents according to
the user's preferred locale.
For monolingual Internet applications, the locale of the user is always fixed and
usually follows the default locale of the runtime environment. Hence the locale
configuration is much simpler.
The following sections describe some of the most common issues that developers
encounter when building a global Internet application:
■

Locale Determination

■

Locale Awareness

■

Localizing the Content

Oracle Globalization Development Kit

8-5

Developing a Global Internet Application

Locale Determination
To be locale-aware or locale-sensitive, Internet applications need to be able to
determine the preferred locale of the user.
Monolingual applications always serve users with the same locale, and that locale
should be equivalent to the default runtime locale of the corresponding programming
environment.
Multilingual applications can determine a user locale dynamically in three ways. Each
method has advantages and disadvantages, but they can be used together in the
applications to complement each other. The user locale can be determined in the
following ways:
■

Based on the user profile information from a LDAP directory server such as the
Oracle Internet Directory or other user profile tables stored inside the database
The schema for the user profile should include preferred locale attribute to
indicate the locale of a user. This way of determining a locale user does not work if
a user has not been logged on before.

■

Based on the default locale of the browser
Get the default ISO locale setting from a browser. The default ISO locale of the
browser is sent through the Accept-Language HTTP header in every HTTP
request. If the Accept-Language header is NULL, then the desired locale should
default to English. The drawback of this approach is that the Accept-Language
header may not be a reliable source of information for the locale of a user.

■

Based on user selection
Allow users to select a locale from a list box or from a menu, and switch the
application locale to the one selected.

The Globalization Development Kit provides an application framework that enables
you to use these locale determination methods declaratively.
"Getting Started with the Globalization Development
Kit" on page 8-7

See Also:

Locale Awareness
To be locale-aware or locale-sensitive, Internet applications need to determine the
locale of a user. After the locale of a user is determined, applications should:
■

Construct HTML content in the language of the locale

■

Use the cultural conventions implied by the locale

Locale-sensitive functions, such as date, time, and monetary formatting, are built into
various programming environments such as Java and PL/SQL. Applications may use
them to format the HTML pages according to the cultural conventions of the locale of
a user. A locale is represented differently in different programming environments. For
example, the French (Canada) locale is represented in different environments as
follows:
■

■

In the ISO standard, it is represented by fr-CA where fr is the language code
defined in the ISO 639 standard and CA is the country code defined in the ISO 3166
standard.
In Java, it is represented as a Java locale object constructed with fr, the ISO
language code for French, as the language and CA, the ISO country code for
Canada, as the country. The Java locale name is fr_CA.

8-6 Oracle Database Globalization Support Guide

Getting Started with the Globalization Development Kit

■

In PL/SQL and SQL, it is represented mainly by the NLS_LANGUAGE and NLS_
TERRITORY session parameters where the value of the NLS_LANGUAGE parameter
is equal to CANADIAN FRENCH and the value of the NLS_TERRITORY parameter
is equal to CANADA.

If you write applications for more than one programming environment, then locales
must be synchronized between environments. For example, Java applications that call
PL/SQL procedures should map the Java locales to the corresponding NLS_LANGUAGE
and NLS_TERRITORY values and change the parameter values to match the user's
locale before calling the PL/SQL procedures.
The Globalization Development Kit for Java provides a set of Java classes to ensure
consistency on locale-sensitive behaviors with Oracle databases.

Localizing the Content
For the application to support a multilingual environment, it must be able to present
the content in the preferred language and in the locale convention of the user.
Hard-coded user interface text must first be externalized from the application, together
with any image files, so that they can be translated into the different languages
supported by the application. The translation files then must be staged in separate
directories, and the application must be able to locate the relevant content according to
the user locale setting. Special application handling may also be required to support a
fallback mechanism, so that if the user-preferred locale is not available, then the next
most suitable content is presented. For example, if Canadian French content is not
available, then it may be suitable for the application to switch to the French files
instead.

Getting Started with the Globalization Development Kit
The Globalization Development Kit (GDK) for Java provides a J2EE application
framework and Java APIs to develop globalized Internet applications using the best
globalization practices and features designed by Oracle. It reduces the complexities
and simplifies the code that Oracle developers require to develop globalized Java
applications.
GDK for Java complements the existing globalization features in J2EE. Although the
J2EE platform already provides a strong foundation for building globalized
applications, its globalization functionalities and behaviors can be quite different from
Oracle's functionalities. GDK for Java provides synchronization of locale-sensitive
behaviors between the middle-tier Java application and the database server.
GDK for PL/SQL contains a suite of PL/SQL packages that provide additional
globalization functionalities for applications written in PL/SQL.
Figure 8–3 shows the major components of the GDK and how they are related to each
other. User applications run on the J2EE container of Oracle Application Server in the
middle tier. GDK provides the application framework that the J2EE application uses to
simplify coding to support globalization. Both the framework and the application call
the GDK Java API to perform locale-sensitive tasks. GDK for PL/SQL offers PL/SQL
packages that help to resolve globalization issues specific to the PL/SQL environment.

Oracle Globalization Development Kit

8-7

Getting Started with the Globalization Development Kit

Figure 8–3 GDK Components
Client-Tier
Browser

Middle-Tier
Application

Server-Tier
Database

Request
Oracle Application Server
Containers for J2EE
Response

GDK
PL / SQL

J2EE User
Application

GDK
Framework for J2EE

GDK - Java API

LDAP

The functionalities offered by GDK for Java can be divided into two categories:
■

■

The GDK application framework for J2EE provides the globalization framework
for building J2EE-based Internet application. The framework encapsulates the
complexity of globalization programming, such as determining user locale,
maintaining locale persistency, and processing locale information. It consists of a
set of Java classes through which applications can gain access to the framework.
These associated Java classes enable applications to code against the framework so
that globalization behaviors can be extended declaratively.
The GDK Java API offers development support in Java applications and provides
consistent globalization operations as provided in Oracle database servers. The
API is accessible and is independent of the GDK framework so that standalone
Java applications and J2EE applications that are not based on the GDK framework
are able to access the individual features offered by the Java API. The features
provided in the Java API include data and number formatting, sorting, and
handling character sets in the same way as the Oracle Database.
The GDK Java API is certified with JDK versions 1.3 and
later with the following exception: The character set conversion
classes depend on the java.nio.charset package, which is
available in JDK 1.4 and later.

Note:

GDK for Java is contained in nine .jar files, all in the form of orai18n*jar. These
files are shipped with the Oracle Database, in the $ORACLE_HOME/jlib directory. If
the application using the GDK is not hosted on the same machine as the database, then

8-8 Oracle Database Globalization Support Guide

GDK Quick Start

the GDK files must be copied to the application server and included into the
CLASSPATH to run your application. You do not need to install the Oracle Database
into your application server to be able to run the GDK inside your Java application.
GDK is a pure Java library that runs on every platform. The Oracle client parameters
NLS_LANG and ORACLE_HOME are not required.

GDK Quick Start
This section explains how to modify a monolingual application to be a global,
multilingual application using GDK. The subsequent sections in this chapter provide
detailed information on using GDK.
Figure 8–4 shows a screenshot from a monolingual Web application.
Figure 8–4 Original HelloWorld Web Page

The initial, non-GDK HelloWorld Web application simply prints a "Hello World!"
message, along with the current date and time in the top right hand corner of the page.
The following code shows the original HelloWorld JSP source code for the preceding
image.
Example 8–1 HelloWorld JSP Page Code
<%@ page contentType="text/html;charset=windows-1252"%>

Hello World Demo

<%= new java.util.Date(System.currentTimeMillis()) %>

Hello World!

The following code example shows the corresponding Web application descriptor file
for the HelloWorld message.

Oracle Globalization Development Kit

8-9

GDK Quick Start

Example 8–2 HelloWorld web.xml Code

web.xml file for the monolingual Hello World

html
text/html

txt
text/plain

The HelloWorld JSP code in Example 8–1 is only for English-speaking users. Some of
the problems with this code are as follows:
■

There is no locale determination based on user preference or browser setting.

■

The title and the heading are included in the code.

■

The date and time value is not localized based on any locale preference.

■

The character encoding included in the code is for Latin-1.

The GDK framework can be integrated into the HelloWorld code to make it a global,
multilingual application. The preceding code can be modified to include the following
features:
■

■

Automatic locale negotiation to detect the user's browser locale and serve the
client with localized HTML pages. The supported application locales are
configured in the GDK configuration file.
Locale selection list to map the supported application locales. The list can have
application locale display names which are the name of the country representing
the locale. The list will be included on the Web page so users can select a different
locale.
GDK framework and API for globalization support for the HelloWorld JSP. This
involves selecting display strings in a locale-sensitive manner and formatting the
date and time value.

Modifying the HelloWorld Application
This section explains how to modify the HelloWorld application to support
globalization. The application will be modified to support three locales, Simplified
Chinese (zh-CN), Swiss German (de-CH), and American English (en-US). The
following rules will be used for the languages:
■

■

If the client locale supports one of these languages, then that language will be used
for the application.
If the client locale does not support one of these languages, then American English
will be used for the application.

8-10 Oracle Database Globalization Support Guide

GDK Quick Start

In addition, the user will be able to change the language by selecting a supported
locales from the locale selection list. The following tasks describe how to modify the
application:
■

Task 1: Enable the Hello World Application to use the GDK Framework

■

Task 2: Configure the GDK Framework for Hello World

■

Task 3: Enable the JSP or Java Servlet

■

Task 4: Create the Locale Selection List

■

Task 5: Build the Application

Task 1: Enable the Hello World Application to use the GDK Framework
In this task, the GDK filter and a listener are configured in the Web application
deployment descriptor file, web.xml. This allows the GDK framework to be used with
the HelloWorld application. Example 8–3 shows the GDK-enabled web.xml file.
Example 8–3 The GDK-enabled web.xml File

web.xml file for Hello World

GDKFilter
oracle.i18n.servlet.filter.ServletFilter

GDKFilter
*.jsp

oracle.i18n.servlet.listener.ContextListener

html
text/html

txt
text/plain

The following tags were added to the file:
■

The filter name is GDKFilter, and the filter class is
oracle.i18n.servlet.filter.ServletFilter.

■

Oracle Globalization Development Kit 8-11

GDK Quick Start

The GDKFilter is specified in the tag, as well as the URL pattern.
■

The listener class is oracle.i18n.servlet.listener.ContextListener.
The default GDK listener is configured to instantiate GDK ApplicationContext,
which controls application scope operations for the framework.

Task 2: Configure the GDK Framework for Hello World
The GDK application framework is configured with the application configuration file
gdkapp.xml. The configuration file is located in the same directory as the web.xml
file. Example 8–4 shows the gdkapp.xml file.
Example 8–4 GDK Configuration File gdkapp.xml

UTF-8

de-CH
en-US
zh-CN

oracle.i18n.servlet.localesource.UserInput
oracle.i18n.servlet.localesource.HttpAcceptLanguage

com.oracle.demo.Messages

The file must be configured for J2EE applications. The following tags are used in the
file:
■

The page encoding tag specifies the character set used for HTTP requests and
responses. The UTF-8 encoding is used as the default because many languages can
be represented by this encoding.

■

Configuring the application locales in the gdkapp.xml file makes a central place
to define locales. This makes it easier to add and remove locales without changing
source code. The locale list can be retrieved using the GDK API call
ApplicationContext.getSupportedLocales.

■

The language of the initial page is determined by the language setting of the
browser. The user can override this language by choosing from the list. The

8-12 Oracle Database Globalization Support Guide

GDK Quick Start

locale-determine-rule is used by GDK to first try the Accept-Language
HTTP header as the source of the locale. If the user selects a locale from the list,
then the JSP posts a locale parameter value containing the selected locale. The
GDK then sends a response with the contents in the selected language.
■

The message resource bundles allow an application access to localized static
content that may be displayed on a Web page. The GDK framework configuration
file allows an application to define a default resource bundle for translated text for
various languages. In the HelloWorld example, the localized string messages are
stored in the Java ListResourceBundle bundle named Messages. The Messages
bundle consists of base resources for the application which are in the default
locale. Two more resource bundles provide the Chinese and German translations.
These resource bundles are named Messages_zh_CN.java and Messages_
de.java respectively. The HelloWorld application will select the right translation
for "Hello World!" from the resource bundle based on the locale determined by the
GDK framework. The tag is used to configure the resource
bundles that the application will use.

Task 3: Enable the JSP or Java Servlet
JSPs and Java servlets must be enabled to use the GDK API. Example 8–5 shows a JSP
that has been modified to enable to use the GDK API and services. This JSP can
accommodate any language and locale.
Example 8–5 Enabled HelloWorld JSP
. . .

<%= localizer.getMessage("helloWorldTitle") %>

<% Date currDate= new Date(System.currentTimeMillis()); %>
<%=localizer.formatDateTime(currDate, OraDateFormat.LONG)%>

<%= localizer.getMessage("helloWorld") %>

Figure 8–5 shows the HelloWorld application that has been configured with the zh-CN
locale as the primary locale for the browser preference. The HelloWorld string and
page title are displayed in Simplified Chinese. In addition, the date is formatted in the
zh-CN locale convention. This example allows the user to override the locale from the
locale selection list.
Oracle Globalization Development Kit 8-13

GDK Quick Start

Figure 8–5 HelloWorld Localized for the zh-CN Locale

When the locale changes or is initialized using the HTTP Request Accept-Language
header or the locale selection list, the GUI behaves appropriately for that locale. This
means the date and time value in the upper right corner is localized properly. In
addition, the strings are localized and displayed on the HelloWorld page.
The GDK Java Localizer class provides capabilities to localize the contents of a Web
page based on the automatic detection of the locale by the GDK framework.
The following code retrieves an instance of the localizer based on the current
HTTPServletRequest object. In addition, several imports are declared for use of the
GDK API within the JSP page. The localizer retrieves localized strings in a
locale-sensitive manner with fallback behavior, and formats the date and time.
<%@page contentType="text/html;charset=UTF-8"%>
<%@page import="java.util.*, oracle.i18n.servlet.*" %>
<%@page import="oracle.i18n.util.*, oracle.i18n.text.*" %>
<%
Localizer localizer = ServletHelper.getLocalizerInstance(request);
%>

The following code retrieves the current date and time value stored in the currDate
variable. The value is formatted by the localizer formatDateTime method. The
OraDateFormat.LONG parameter in the formatDateTime method instructs the
localizer to format the date using the locale's long formatting style. If the locale of the
incoming request is changed to a different locale with the locale selection list, then the
date and time value will be formatted according to the conventions of the new locale.
No code changes need to be made to support newly-introduced locales.
div style="color: blue;" align="right">
<% Date currDate= new Date(System.currentTimeMillis()); %>
<%=localizer.formatDateTime(currDate, OraDateFormat.LONG)%>

The HelloWorld JSP can be reused for any locale because the HelloWorld string and title are selected in a locale-sensitive manner. The translated strings are selected from a resource bundle. 8-14 Oracle Database Globalization Support Guide GDK Quick Start The GDK uses the OraResourceBundle class for implementing the resource bundle fallback behavior. The following code shows how the Localizer picks the HelloWorld message from the resource bundle. The default application resource bundle Messages is declared in the gdkapp.xml file. The localizer uses the message resource bundle to pick the message and apply the locale-specific logic. For example, if the current locale for the incoming request is "de-CH", then the message will first be looked for in the messages_de_CH bundle. If it does not exist, then it will look up in the Messages_de resource bundle.

<%= localizer.getMessage("helloWorld") %>

Task 4: Create the Locale Selection List The locale selection list is used to override the selected locale based on the HTTP Request Accept-Language header. The GDK framework checks the locale parameter passed in as part of the HTTP POST request as a value for the new locale. A locale selected with the locale selection list is posted as the locale parameter value. GDK uses this value for the request locale. All this happens implicitly within the GDK code. The following code sample displays the locale selection list as an HTML select tag with the name locale. The submit tag causes the new value to be posted to the server. The GDK framework retrieves the correct selection. The locale selection list is constructed from the HTML code generated by the getCountryDropDown method. The method converts the configured application locales into localized country names. A call is made to the ServletHelper class to get the ApplicationContext object associated with the current request. This object provides the globalization context for an application, which includes information such as supported locales and configuration information. The getSupportedLocales call retrieves the list of locales in the gdkapp.xml file. The configured application locale list is displayed as options of the HTML select. The OraDisplayLocaleInfo class is responsible for providing localization methods of locale-specific elements such as country and language names. An instance of this class is created by passing in the current locale automatically determined by the GDK framework. GDK creates requests and response wrappers for HTTP request and responses. The request.getLocale() method returns the GDK determined locale based on the locale determination rules. The OraDsiplayLocaleInfo.getDisplayCountry method retrieves the localized country names of the application locales. An HTML option list is created in the ddOptBuffer string buffer. The getCountryDropDown call returns a string containing the following HTML values: In the preceding values, the en-US locale is selected for the locale. Country names are generated are based on the current locale. Oracle Globalization Development Kit 8-15 GDK Application Framework for J2EE Example 8–6 shows the code for constructing the locale selection list. Example 8–6 Constructing the Locale Selection List <%! public String getCountryDropDown(HttpServletRequest request) { StringBuffer ddOptBuffer=new StringBuffer(); ApplicationContext ctx = ServletHelper.getApplicationContextInstance(request); Locale[] appLocales = ctx.getSupportedLocales(); Locale currentLocale = request.getLocale(); if (currentLocale.getCountry().equals("")) { // Since the Country was not specified get the Default Locale // (with Country) from the GDK OraLocaleInfo oli = OraLocaleInfo.getInstance(currentLocale); currentLocale = oli.getLocale(); } OraDisplayLocaleInfo odli = OraDisplayLocaleInfo.getInstance(currentLocale); for (int i=0;i" + odli.getDisplayCountry(appLocales[i]) + " [" + appLocales[i] + "]\n"); } return ddOptBuffer.toString(); } %> Task 5: Build the Application In order to build the application, the following files must be specified in the classpath: ■ orai18n.jar ■ regexp.jar The orai18n.jar file contains the GDK framework and the API. The regexp.jar file contains the regular expression library. The GDK API also has locale determination capabilities. The classes are supplied by the ora18n-lcsd.jar file. GDK Application Framework for J2EE GDK for Java provides the globalization framework for middle-tier J2EE applications. The framework encapsulates the complexity of globalization programming, such as determining user locale, maintaining locale persistency, and processing locale information. This framework minimizes the effort required to make Internet applications global-ready. The GDK application framework is shown in Figure 8–6. 8-16 Oracle Database Globalization Support Guide GDK Application Framework for J2EE Figure 8–6 GDK Application Framework for J2EE Response Request GDK Framework for J2EE ServletRequestWrapper ServletResponseWrapper Localizer LocalSource ApplicationContext GDK Configuration File J2EE User Application GDK Java API The main Java classes composing the framework are as follows: ■ ■ ■ ■ ■ ApplicationContext provides the globalization context of an application. The context information includes the list of supported locales and the rule for determining user-preferred locale. The context information is obtained from the GDK application configuration file for the application. The set of LocaleSource classes can be plugged into the framework. Each LocaleSource class implements the LocaleSource interface to get the locale from the corresponding source. Oracle bundles several LocaleSource classes in GDK. For example, the DBLocaleSource class obtains the locale information of the current user from a database schema. You can also write a customized LocaleSource class by implementing the same LocaleSource interface and plugging it into the framework. ServletRequestWrapper and ServletResponseWrapper are the main classes of the GDK Servlet filter that transforms HTTP requests and HTTP responses. ServletRequestWrapper instantiates a Localizer object for each HTTP request based on the information gathered from the ApplicationContext and LocaleSource objects and ensures that forms parameters are handled properly. ServletResponseWrapper controls how HTTP response should be constructed. Localizer is the all-in-one object that exposes the important functions that are sensitive to the current user locale and application context. It provides a centralized set of methods for you to call and make your applications behave appropriately to the current user locale and application context. The GDK Java API is always available for applications to enable finer control of globalization behavior. The GDK application framework simplifies the coding required for your applications to support different locales. When you write a J2EE application according to the application framework, the application code is independent of what locales the application supports, and you control the globalization support in the application by Oracle Globalization Development Kit 8-17 GDK Application Framework for J2EE defining it in the GDK application configuration file. There is no code change required when you add or remove a locale from the list of supported application locales. The following list gives you some idea of the extent to which you can define the globalization support in the GDK application configuration file: ■ You can add and remove a locale from the list of supported locales. ■ You can change the way the user locale is determined. ■ You can change the HTML page encoding of your application. ■ You can specify how the translated resources can be located. ■ You can plug a new LocaleSource object into the framework and use it to detect a user locale. This section includes the following topics: ■ Making the GDK Framework Available to J2EE Applications ■ Integrating Locale Sources into the GDK Framework ■ Getting the User Locale From the GDK Framework ■ Implementing Locale Awareness Using the GDK Localizer ■ Defining the Supported Application Locales in the GDK ■ Handling Non-ASCII Input and Output in the GDK Framework ■ Managing Localized Content in the GDK Making the GDK Framework Available to J2EE Applications The behavior of the GDK application framework for J2EE is controlled by the GDK application configuration file, gdkapp.xml. The application configuration file allows developers to specify the behaviors of globalized applications in one centralized place. One application configuration file is required for each J2EE application using the GDK. The gdkapp.xml file should be placed in the ./WEB-INF directory of the J2EE environment of the application. The file dictates the behavior and the properties of the GDK framework and the application that is using it. It contains locale mapping tables, character sets of content files, and globalization parameters for the configuration of the application. The application administrator can modify the application configuration file to change the globalization behavior in the application, without needing to change the programs and to recompile them. See Also: "The GDK Application Configuration File" on page 8-35 For a J2EE application to use the GDK application framework defined by the corresponding GDK application configuration file, the GDK Servlet filter and the GDK context listener must be defined in the web.xml file of the application. The web.xml file should be modified to include the following at the beginning of the file:

gdkfilter

oracle.i18n.servlet.filter.ServletFilter

gdkfilter

*.jsp 8-18 Oracle Database Globalization Support Guide GDK Application Framework for J2EE

oracle.i18n.servlet.listener.ContextListener

Examples of the gdkapp.xml and web.xml files can be found in the $ORACLE_ HOME/nls/gdk/demo directory. The GDK application framework supports Servlet container version 2.3 and later. It uses the Servlet filter facility for transparent globalization operations such as determining the user locale and specifying the character set for content files. The ContextListener instantiates GDK application parameters described in the GDK application configuration file. The ServletFilter overrides the request and response objects with a GDK request (ServletRequestWrapper) and response (ServletResponseWrapper) objects, respectively. If other application filters are used in the application to also override the same methods, then the filter in the GDK framework may return incorrect results. For example, if getLocale returns en_US, but the result is overridden by other filters, then the result of the GDK locale detection mechanism is affected. All of the methods that are being overridden in the filter of the GDK framework are documented in Oracle Globalization Development Kit Java API Reference. Be aware of potential conflicts when using other filters together with the GDK framework. Integrating Locale Sources into the GDK Framework Determining the user's preferred locale is the first step in making an application global-ready. The locale detection offered by the J2EE application framework is primitive. It lacks the method that transparently retrieves the most appropriate user locale among locale sources. It provides locale detection by the HTTP language preference only, and it cannot support a multilevel locale fallback mechanism. The GDK application framework provides support for predefined locale sources to complement J2EE. In a web application, several locale sources are available. Table 8–1 summarizes locale sources that are provided by the GDK. Table 8–1 Locale Resources Provided by the GDK Locale Description HTTP language preference Locales included in the HTTP protocol as a value of Accept-Language. This is set at the web browser level. A locale fallback operation is required if the browser locale is not supported by the application. User input locale Locale specified by the user from a menu or a parameter in the HTTP protocol User profile locale preference Locale preference stored in the database as part of the user profiles from database Application default locale A locale defined in the GDK application configuration file. This locale is defined as the default locale for the application. Typically, this is used as a fallback locale when the other locale sources are not available. See Also: "The GDK Application Configuration File" on page 8-35 for information about the GDK multilevel locale fallback mechanism Oracle Globalization Development Kit 8-19 GDK Application Framework for J2EE The GDK application framework provides seamless support for predefined locale sources, such as user input locale, HTTP language preference, user profile locale preference in the database, and the application default locale. You can incorporate the locale sources to the framework by defining them under the tag in the GDK application configuration file as follows:

oracle.i18n.servlet.localesource.UserInput

oracle.i18n.servlet.localesource.HTTPAcceptLanguage

The GDK framework uses the locale source declaration order and determines whether a particular locale source is available. If it is available, then it is used as the source, otherwise, it tries to find the next available locale source for the list. In the preceding example, if the UserInput locale source is available, it is used first, otherwise, the HTTPAcceptLanguage locale source will be used. Custom locale sources, such as locale preference from an LDAP server, can be easily implemented and integrated into the GDK framework. You need to implement the LocaleSource interface and specify the corresponding implementation class under the tag in the same way as the predefined locale sources were specified. The LocaleSource implementation not only retrieves the locale information from the corresponding source to the framework but also updates the locale information to the corresponding source when the framework tells it to do so. Locale sources can be read-only or read/write, and they can be cacheable or noncacheable. The GDK framework initiates updates only to read/write locale sources and caches the locale information from cacheable locale sources. Examples of custom locale sources can be found in the $ORACLE_HOME/nls/gdk/demo directory. See Also: Oracle Globalization Development Kit Java API Reference for more information about implementing a LocaleSource Getting the User Locale From the GDK Framework The GDK offers automatic locale detection to determine the current locale of the user. For example, the following code retrieves the current user locale in Java. It uses a Locale object explicitly. Locale loc = request.getLocale(); The getLocale() method returns the Locale that represents the current locale. This is similar to invoking the HttpServletRequest.getLocale() method in JSP or Java Servlet code. However, the logic in determining the user locale is different, because multiple locale sources are being considered in the GDK framework. Alternatively, you can get a Localizer object that encapsulates the Locale object determined by the GDK framework. For the benefits of using the Localizer object, see "Implementing Locale Awareness Using the GDK Localizer" on page 8-21. Localizer localizer = ServletHelper.getLocalizerInstance(request); Locale loc = localizer.getLocale(); The locale detection logic of the GDK framework depends on the locale sources defined in the GDK application configuration file. The names of the locale sources are registered in the application configuration file. The following example shows the locale determination rule section of the application configuration file. It indicates that the user-preferred locale can be determined from either the LDAP server or from the 8-20 Oracle Database Globalization Support Guide GDK Application Framework for J2EE HTTP Accept-Language header. The LDAPUserSchema locale source class should be provided by the application. Note that all of the locale source classes have to be extended from the LocaleSource abstract class.

LDAPUserSchema

oracle.i18n.localesource.HTTPAcceptLanguage

For example, when the user is authenticated in the application and the user locale preference is stored in an LDAP server, then the LDAPUserSchema class connects to the LDAP server to retrieve the user locale preference. When the user is anonymous, then the HttpAcceptLanguage class returns the language preference of the web browser. The cache is maintained for the duration of a HTTP session. If the locale source is obtained from the HTTP language preference, then the locale information is passed to the application in the HTTP Accept-Language header and not cached. This enables flexibility so that the locale preference can change between requests. The cache is available in the HTTP session. The GDK framework exposes a method for the application to overwrite the locale preference information persistently stored in locale sources such as the LDAP server or the user profile table in the database. This method also resets the current locale information stored inside the cache for the current HTTP session. The following is an example of overwriting the preferred locale using the store command. To discard the current locale information stored inside the cache, the clean command can be specified as the input parameter. The following table shows the list of commands supported by the GDK: Command Functionality store Updates user locale preferences in the available locale sources with the specified locale information. This command is ignored by the read-only locale sources. clean Discards the current locale information in the cache. Note that the GDK parameter names can be customized in the application configuration file to avoid name conflicts with other parameters used in the application. Implementing Locale Awareness Using the GDK Localizer The Localizer object obtained from the GDK application framework is an all-in-one globalization object that provides access to functions that are commonly used in building locale awareness in your applications. In addition, it provides functions to get information about the application context, such as the list of supported locales. The Localizer object simplifies and centralizes the code required to build consistent locale awareness behavior in your applications. The oracle.i18n.servlet package contains the Localizer class. You can get the Localizer instance as follows: Localizer lc = ServletHelper.getLocalizerInstance(request); Oracle Globalization Development Kit 8-21 GDK Application Framework for J2EE The Localizer object encapsulates the most commonly used locale-sensitive information determined by the GDK framework and exposes it as locale-sensitive methods. This object includes the following functionalities pertaining to the user locale: ■ Format date in long and short formats ■ Format numbers and currencies ■ Get collation key value of a string ■ Get locale data such as language, country and currency names ■ Get locale data to be used for constructing user interface ■ Get a translated message from resource bundles ■ Get text formatting information such as writing direction ■ Encode and decode URLs ■ Get the common list of time zones and linguistic sorts For example, when you want to display a date in your application, you may want to call the Localizer.formatDate() or Localizer.formateDateTime() methods. When you want to determine the writing direction of the current locale, you can call the Localizer.getWritingDirection() and Localizer.getAlignment() to determine the value used in the tag and tag respectively. The Localizer object also exposes methods to enumerate the list of supported locales and their corresponding languages and countries in your applications. The Localizer object actually makes use of the classes in the GDK Java API to accomplish its tasks. These classes include, but are not limited to, the following: OraDateFormat, OraNumberFormat, OraCollator, OraLocaleInfo, oracle.i18n.util.LocaleMapper, oracle.i18n.net.URLEncoder, and oracle.i18n.net.URLDecoder. The Localizer object simplifies the code you need to write for locale awareness. It maintains caches of the corresponding objects created from the GDK Java API so that the calling application does not need to maintain these objects for subsequent calls to the same objects. If you require more than the functionality the Localizer object can provide, then you can always call the corresponding methods in the GDK Java API directly. See Also: Oracle Globalization Development Kit Java API Reference for detailed information about the Localizer object Defining the Supported Application Locales in the GDK The number of locales and the names of the locales that an application needs to support are based on the business requirements of the application. The names of the locales that are supported by the application are registered in the application configuration file. The following example shows the application locales section of the application configuration file. It indicates that the application supports German (de), Japanese (ja), and English for the US (en-US), with English defined as the default fallback application locale. Note that the locale names are based on the IANA convention. de 8-22 Oracle Database Globalization Support Guide GDK Application Framework for J2EE ja en-US When the GDK framework detects the user locale, it verifies whether the locale that is returned is one of the supported locales in the application configuration file. The verification algorithm is as follows: 1. Retrieve the list of supported application locales from the application configuration file. 2. Check whether the locale that was detected is included in the list. If it is included in the list, then use this locale as the current client's locale. 3. If there is a variant in the locale that was detected, then remove the variant and check whether the resulting locale is in the list. For example, the Java locale de_ DE_EURO has a EURO variant. Remove the variant so that the resulting locale is de_DE. 4. If the locale includes a country code, then remove the country code and check whether the resulting locale is in the list. For example, the Java locale de_DE has a country code of DE. Remove the country code so that the resulting locale is de. 5. If the detected locale does not match any of the locales in the list, then use the default locale that is defined in the application configuration file as the client locale. By performing steps 3 and 4, the application can support users with the same language requirements but with different locale settings than those defined in the application configuration file. For example, the GDK can support de-AT (the Austrian variant of German), de-CH (the Swiss variant of German), and de-LU (the Luxembourgian variant of German) locales. The locale fallback detection in the GDK framework is similar to that of the Java Resource Bundle, except that it is not affected by the default locale of the Java VM. This exception occurs because the Application Default Locale can be used during the GDK locale fallback operations. If the application-locales section is omitted from the application configuration file, then the GDK assumes that the common locales, which can be returned from the OraLocaleInfo.getCommonLocales method, are supported by the application. Handling Non-ASCII Input and Output in the GDK Framework The character set (or character encoding) of an HTML page is a very important piece of information to a browser and an Internet application. The browser needs to interpret this information so that it can use correct fonts and character set mapping tables for displaying pages. The Internet applications need to know so they can safely process input data from a HTML form based on the specified encoding. The page encoding can be translated as the character set used for the locale to which an Internet application is serving. In order to correctly specify the page encoding for HTML pages without using the GDK framework, Internet applications must: 1. Determine the desired page input data character set encoding for a given locale. 2. Specify the corresponding encoding name for each HTTP request and HTTP response. Oracle Globalization Development Kit 8-23 GDK Application Framework for J2EE Applications using the GDK framework can ignore these steps. No application code change is required. The character set information is specified in the GDK application configuration file. At runtime, the GDK automatically sets the character sets for the request and response objects. The GDK framework does not support the scenario where the incoming character set is different from that of the outgoing character set. The GDK application framework supports the following scenarios for setting the character sets of the HTML pages: ■ ■ ■ A single local character set is dedicated to the whole application. This is appropriate for a monolingual Internet application. Depending on the properties of the character set, it may be able to support more than one language. For example, most Western European languages can be served by ISO-8859-1. Unicode UTF-8 is used for all contents regardless of the language. This is appropriate for a multilingual application that uses Unicode for deployment. The native character set for each language is used. For example, English contents are represented in ISO-8859-1, and Japanese contents are represented in Shift_JIS. This is appropriate for a multilingual Internet application that uses a default character set mapping for each locale. This is useful for applications that need to support different character sets based on the user locales. For example, for mobile applications that lack Unicode fonts or Internet browsers that cannot fully support Unicode, the character sets must to be determined for each request. The character set information is specified in the GDK application configuration file. The following is an example of setting UTF-8 as the character set for all the application pages. UTF-8 The page character set information is used by the ServletRequestWrapper class, which sets the proper character set for the request object. It is also used by the ContentType HTTP header specified in the ServletResponseWrapper class for output when instantiated. If page-charset is set to AUTO-CHARSET, then the character set is assumed to be the default character set for the current user locale. Set page-charset to AUTO-CHARSET as follows: AUTO-CHARSET The default mappings are derived from the LocaleMapper class, which provides the default IANA character set for the locale name in the GDK Java API. Table 8–2 lists the mappings between the common ISO locales and their IANA character sets. Table 8–2 Mapping Between Common ISO Locales and IANA Character Sets ISO Locale NLS_LANGUAGE Value NLS_TERRITORY Value IANA Character Set ar-SA ARABIC SAUDI ARABIA WINDOWS-1256 de-DE GERMAN GERMANY WINDOWS-1252 en-US AMERICAN AMERICA WINDOWS-1252 en-GB ENGLISH UNITED KINGDOM WINDOWS-1252 el GREEK GREECE WINDOWS-1253 es-ES SPANISH SPAIN WINDOWS-1252 fr FRENCH FRANCE WINDOWS-1252 fr-CA CANADIAN FRENCH CANADA WINDOWS-1252 8-24 Oracle Database Globalization Support Guide GDK Application Framework for J2EE Table 8–2 (Cont.) Mapping Between Common ISO Locales and IANA Character Sets ISO Locale NLS_LANGUAGE Value NLS_TERRITORY Value IANA Character Set iw HEBREW ISRAEL WINDOWS-1255 ko KOREAN KOREA EUC-KR ja JAPANESE JAPAN SHIFT_JIS it ITALIAN ITALY WINDOWS-1252 pt PORTUGUESE PORTUGAL WINDOWS-1252 pt-BR BRAZILIAN PORTUGUESE BRAZIL WINDOWS-1252 tr TURKISH TURKEY WINDOWS-1254 nl DUTCH THE NETHERLANDS WINDOWS-1252 zh SIMPLIFIED CHINESE CHINA GBK zh-TW TRADITIONAL CHINESE TAIWAN BIG5 The locale to character set mapping in the GDK can also be customized. To override the default mapping defined in the GDK Java API, a locale-to-character-set mapping table can be specified in the application configuration file.

jaEUC-JP

The previous example shows that for locale Japanese (ja), the GDK changes the default character set from SHIFT_JIS to EUC-JP. See Also: "Oracle Locale Information in the GDK" on page 8-28 Managing Localized Content in the GDK This section includes the following topics: ■ Managing Localized Content in JSPs and Java Servlets ■ Managing Localized Content in Static Files Managing Localized Content in JSPs and Java Servlets Resource bundles enable access to localized contents at runtime in J2SE. Translatable strings within Java servlets and Java Server Pages (JSPs) are externalized into Java resource bundles so that these resource bundles can be translated independently into different languages. The translated resource bundles carry the same base class names as the English bundles, using the Java locale name as the suffix. To retrieve translated data from the resource bundle, the getBundle() method must be invoked for every request. <% Locale user_locale=request.getLocale(); ResourceBundle rb=ResourceBundle.getBundle("resource",user_locale); %> <%= rb.getString("Welcome") %> The GDK framework simplifies the retrieval of text strings from the resource bundles. Localizer.getMessage() is a wrapper to the resource bundle. Oracle Globalization Development Kit 8-25 GDK Application Framework for J2EE <% Localizer.getMessage ("Welcome") %> Instead of specifying the base class name as getBundle() in the application, you can specify the resource bundle in the application configuration file, so that the GDK automatically instantiates a ResourceBundle object when a translated text string is requested.

resource

This configuration file snippet declares a default resource bundle whose translated contents reside in the "resource" Java bundle class. Multiple resource bundles can be specified in the configuration file. To access a nondefault bundle, specify the name parameter in the getMessage method. The message bundle mechanism uses the OraResourceBundle GDK class for its implementation. This class provides the special locale fallback behaviors on top of the Java behaviors. The rules are as follows: ■ ■ ■ ■ ■ ■ If the given locale exactly matches the locale in the available resource bundles, it will be used. If the resource bundle for Chinese in Singapore (zh_SG) is not found, it will fall back to the resource bundle for Chinese in China (zh_CN) for Simplified Chinese translations. If the resource bundle for Chinese in Hong Kong (zh_HK) is not found, it will fall back to the resource bundle for Chinese in Taiwan (zh_TW) for Traditional Chinese translations. If the resource bundle for Chinese in Macau (zh_MO) is not found, it will fall back to the resource bundle for Chinese in Taiwan (zh_TW) for Traditional Chinese translations. If the resource bundle for any other Chinese (zh_ and zh) is not found, it will fall back to the resource bundle for Chinese in China (zh_CN) for Simplified Chinese translations. The default locale, which can be obtained by the Locale.getDefault() method, will not be considered in the fallback operations. For example, assume the default locale is ja_JP and the resource handle for it is available. When the resource bundle for es_MX is requested, and neither resource bundle for es or es_MX is provided, the base resource bundle object that does not have a local suffix is returned. The usage of the OraResourceBundle class is similar to the java.util.ResourceBundle class, but the OraResearchBundle class does not instantiate itself. Instead, the return value of the getBundle method is an instance of the subclass of the java.util.ResourceBundle class. Managing Localized Content in Static Files For a application, which supports only one locale, the URL that has a suffix of /index.html typically takes the user to the starting page of the application. In a globalized application, contents in different languages are usually stored separately, and it is common for them to be staged in different directories or with different file names based on the language or the country name. This information is then used to construct the URLs for localized content retrieval in the application. The following examples illustrate how to retrieve the French and Japanese versions of the index page. Their suffixes are as follows: 8-26 Oracle Database Globalization Support Guide GDK Java API /fr/index.html /ja/index.html By using the rewriteURL() method of the ServletHelper class, the GDK framework handles the logic to locate the translated files from the corresponding language directories. The ServletHelper.rewriteURL() method rewrites a URL based on the rules specified in the application configuration file. This method is used to determine the correct location where the localized content is staged. The following is an example of the JSP code:

^Mozilla⁄ 4.0

ISO-8859-1 The previous example shows that if the user-agent value in the HTTP header starts with Mozilla/4.0 (which indicates an older version of Web clients) for English (en) and German (de) locales, then the GDK sets the character set to ISO-8859-1. Multiple locales can be specified in a comma-delimited list. See Also: "page-charset" on page 8-36 page-charset This tag section defines the character set of the application pages. If this is explicitly set to a given character set, then all pages use this character set. The character set name must follow the IANA character set convention, for example: UTF-8 However, if the page-charset is set to AUTO-CHARSET, then the character set is based on the default character set of the current user locale. The default character set is derived from the locale to character set mapping table specified in the application configuration file. If the character set mapping table in the application configuration file is not available, then the character set is based on the default locale name to IANA character set mapping table in the GDK. Default mappings are derived from OraLocaleInfo class. See Also: ■ ■ "locale-charset-maps" on page 8-35 "Handling Non-ASCII Input and Output in the GDK Framework" on page 8-23 application-locales This tag section defines a list of the locales supported by the application. For example: en-US de zh-CN If the language component is specified with the * country code, then all locale names with this language code qualify. For example, if de-* (the language code for German) is defined as one of the application locales, then this supports de-AT (GermanAustria), de (German-Germany), de-LU (German-Luxembourg), de-CH 8-36 Oracle Database Globalization Support Guide The GDK Application Configuration File (German-Switzerland), and even irregular locale combination such as de-CN (German-China). However, the application can be restricted to support a predefined set of locales. It is recommended to set one of the application locales as the default application locale (by specifying default="yes") so that it can be used as a fall back locale for customers who are connecting to the application with an unsupported locale. locale-determine-rule This section defines the order in which the preferred user locale is determined. The locale sources should be specified based on the scenario in the application. This section includes the following scenarios: ■ Scenario 1: The GDK framework uses the accept language at all times. oracle.i18n.servlet.localesource.HTTPAcceptLanguage ■ Scenario 2: By default, the GDK framework uses the accept language. After the user specifies the locale, the locale is used for further operations. oracle.i18n.servlet.localesource.UserInput oracle.i18n.servlet.localesource.HTTPAcceptLanguage ■ Scenario 3: By default, the GDK framework uses the accept language. After the user is authenticated, the GDK framework uses the database locale source. The database locale source is cached until the user logs out. After the user logs out, the accept language is used again. oracle.i18n.servlet.localesource.DBLocaleSource oracle.i18n.servlet.localesource.HttpAcceptLanguage Note that Scenario 3 includes the predefined database locale source, DBLocaleSource. It enables the user profile information to be specified in the configuration file without writing a custom database locale source. In the example, the user profile table is called "customer". The columns are "customer_email", "nls_language", "nls_territory", and "timezone". They store the unique e-mail address, the Oracle name of the preferred language, the Oracle name of the preferred territory, and the time zone ID of a customer. The user-key is a mandatory attribute that specifies the attribute name used to pass the user ID from the application to the GDK framework. ■ Scenario 4: The GDK framework uses the accept language in the first page. When the user inputs a locale, it is cached and used until the user logs into the application. After the user is authenticated, the GDK framework uses the database locale source. The database locale source is cached until the user logs out. After the user logs out, the accept language is used again or the user input is used if the user inputs a locale. demo.DatabaseLocaleSource

oracle.i18n.servlet.localesource.UserInput

oracle.i18n.servlet.localesource.HttpAcceptLanguage Oracle Globalization Development Kit 8-37 The GDK Application Configuration File Note that Scenario 4 uses the custom database locale source. If the user profile schema is complex, such as user profile information separated into multiple tables, then the custom locale source should be provided by the application. Examples of custom locale sources can be found in the $ORACLE_HOME/nls/gdk/demo directory. locale-parameter-name This tag defines the name of the locale parameters that are used in the user input so that the current user locale can be passed between requests. Table 8–3 shows the parameters used in the GDK framework. Table 8–3 Locale Parameters Used in the GDK Framework Default Parameter Name Value locale ISO locale where ISO 639 language code and ISO 3166 country code are connected with an underscore (_).or a hyphen (-). For example, zh_CN for Simplified Chinese used in China language Oracle language name. For example, AMERICAN for American English territory Oracle territory name. For example, SPAIN timezone Timezone name. For example, American/Los_Angeles iso-currency ISO 4217 currency code. For example, EUR for the euro date-format Date format pattern mask. For example, DD_MON_RRRR long-date-format Long date format pattern mask. For example, DAY-YYY-MM-DD date-time-format Date and time format pattern mask. For example, DD-MON-RRRR HH24:MI:SS long-date-time-format Long date and time format pattern mask. For example, DAY YYYY-MM-DD HH12:MI:SS AM time-format Time format pattern mask. For example, HH:MI:SS number-format Number format. For example, 9G99G990D00 currency-format Currency format. For example, L9G99G990D00 linguistic-sorting Linguistic sort order name. For example, JAPANESE_M for Japanese multilingual sort charset Character set. For example, WE8ISO8859P15 writing-direction Writing direction string. For example, LTR for left-to-right writing direction or RTL for right-to-left writing direction command GDK command. For example, store for the update operation The parameter names are used in either the parameter in the HTML form or in the URL. message-bundles This tag defines the base class names of the resource bundles used in the application. The mapping is used in the Localizer.getMessage method for locating translated text in the resource bundles.

Messages

NewMessages

8-38 Oracle Database Globalization Support Guide The GDK Application Configuration File If the name attribute is not specified or if it is specified as name="default" to the tag, then the corresponding resource bundle is used as the default message bundle. To support more than one resource bundle in an application, resource bundle names must be assigned to the nondefault resource bundles. The nondefault bundle names must be passed as a parameter of the getMessage method. For example: Localizer loc = ServletHelper.getLocalizerInstance(request); String translatedMessage = loc.getMessage("Hello"); String translatedMessage2 = loc.getMessage("World", "newresource"); url-rewrite-rule This tag is used to control the behavior of the URL rewrite operations. The rewriting rule is a regular expression. (.*)/([^/]+)$ $1/$L/$2 See Also: "Managing Localized Content in the GDK" on page 8-25 If the localized content for the requested locale is not available, then it is possible for the GDK framework to trigger the locale fallback mechanism by mapping it to the closest translation locale. By default the fallback option is turned off. This can be turned on by specifying fallback="yes". For example, suppose an application supports only the following translations: en, de, and ja, and en is the default locale of the application. If the current application locale is de-US, then it falls back to de. If the user selects zh-TW as its application locale, then it falls back to en. A fallback mechanism is often necessary if the number of supported application locales is greater than the number of the translation locales. This usually happens if multiple locales share one translation. One example is Spanish. The application may need to support multiple Spanish-speaking countries and not just Spain, with one set of translation files. Multiple URL rewrite rules can be specified by assigning the name attribute to nondefault URL rewrite rules. To use the nondefault URL rewrite rules, the name must be passed as a parameter of the rewrite URL method. For example:

"> The first rule changes the "images/welcome.gif" URL to the localized welcome image file. The second rule named "flag" changes the "US.gif" URL to the user's country flag image file. The rule definition should be as follows: (.*)/([^/]+)$ $1/$L/$2 US.gif/pattern> $C.gif Oracle Globalization Development Kit 8-39 The GDK Application Configuration File Example: GDK Application Configuration File This section contains an example of an application configuration file with the following application properties: ■ The application supports the following locales: Arabic (ar), Greek (el), English (en), German (de), French (fr), Japanese (ja) and Simplified Chinese for China (zh-CN). ■ English is the default application locale. ■ The page character set for the ja locale is always UTF-8. ■ ■ ■ ■ ■ The page character set for the en and de locales when using an Internet Explorer client is windows-1252. The page character set for the en, de, and fr locales on other web browser clients is iso-8859-1. The page character sets for all other locales are the default character set for the locale. The user locale is determined by the following order: user input locale and then Accept-Language. The localized contents are stored in their appropriate language subfolders. The folder names are derived from the ISO 639 language code. The folders are located in the root directory of the application. For example, the Japanese file for /shop/welcome.jpg is stored in /ja/shop/welcome.jpg.

ja UTF-8

en,de

^Mozilla\/[0-9\. ]+$compatible; MSIE [^;]+; $

WINDOWS-1252

en,de,fr ISO-8859-1

AUTO-CHARSET

ar de fr ja el en zh-CN

oracle.i18n.servlet.localesource.UserInput

oracle.i18n.servlet.localesource.HttpAcceptLanguage

8-40 Oracle Database Globalization Support Guide GDK for Java Supplied Packages and Classes

(.*)/([^/]+)$ /$L/$1/$2

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<%= localizer.getMessage("helloWorld") %>

<%= localizer.getMessage("helloWorld") %>

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