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Introduction to Oracle9i: SQL
Student Guide • Volume 2

40049GC10
Production 1.0
June 2001
D33052

Authors

Copyright © Oracle Corporation, 2000, 2001. All rights reserved.

Nancy Greenberg
Priya Nathan

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and Reviewers
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Contents
Preface
Curriculum Map
Introduction
Objectives I-2
Oracle9i I-3
Oracle9i Application Server I-5
Oracle9i Database I-6
Oracle9i: Object Relational Database Management System I-8
Oracle Internet Platform I-9
System Development Life Cycle I-10
Data Storage on Different Media I-12
Relational Database Concept I-13
Definition of a Relational Database I-14
Data Models I-15
Entity Relationship Model I-16
Entity Relationship Modeling Conventions I-17
Relating Multiple Tables I-19
Relational Database Terminology I-20
Relational Database Properties I-21
Communicating with a RDBMS Using SQL I-22
Relational Database Management System I-23
SQL Statements I-24
Tables Used in the Course I-25
Summary I-26

1

Writing Basic SQL SELECT Statements
Objectives 1-2
Capabilities of SQL SELECT Statements 1-3
Basic SELECT Statement 1-4
iii

Selecting All Columns 1-5
Selecting Specific Columns 1-6
Writing SQL Statements 1-7
Column Heading Defaults 1-8
Arithmetic Expressions 1-9
Using Arithmetic Operators 1-10
Operator Precedence 1-11
Using Parentheses 1-13
Defining a Null Value 1-14
Null Values in Arithmetic Expressions 1-15
Defining a Column Alias 1-16
Using Column Aliases 1-17
Concatenation Operator 1-18
Using the Concatenation Operator 1-19
Literal Character Strings 1-20
Using Literal Character Strings 1-21
Duplicate Rows 1-22
Eliminating Duplicate Rows 1-23
SQL and iSQL*Plus Interaction 1-24
SQL Statements versus iSQL*Plus Commands
Overview of iSQL*Plus 1-26
Logging In to iSQL*Plus 1-27
The iSQL*Plus Environment 1-28
Displaying Table Structure 1-29
Interacting with Script Files 1-31
Summary 1-34
Practice 1 Overview 1-35

iv

1-25

2

Restricting and Sorting Data
Objectives 2-2
Limiting Rows Using a Selection 2-3
Limiting the Rows Selected 2-4
Using the WHERE Clause 2-5
Character Strings and Dates 2-6
Comparison Conditions 2-7
Using Comparison Conditions 2-8
Other Comparison Conditions 2-9
Using the BETWEEN Condition 2-10
Using the IN Condition 2-11
Using the LIKE Condition 2-12
Using the NULL Conditions 2-14
Logical Conditions 2-15
Using the AND Operator 2-16
Using the OR Operator 2-17
Using the NOT Operator 2-18
Rules of Precedence 2-19
ORDER BY Clause 2-22
Sorting in Descending Order 2-23
Sorting by Column Alias 2-24
Sorting by Multiple Columns 2-25
Summary 2-26
Practice 2 Overview 2-27

v

3

Single-Row Functions
Objectives 3-2
SQL Functions 3-3
Two Types of SQL Functions 3-4
Single-Row Functions 3-5
Character Functions 3-7
Case Manipulation Functions 3-9
Using Case Manipulation Functions 3-10
Character-Manipulation Functions 3-11
Using the Character-Manipulation Functions 3-12
Number Functions 3-13
Using the ROUND Function 3-14
Using the TRUNC Function 3-15
Using the MOD Function 3-16
Working with Dates 3-17
Arithmetic with Dates 3-19
Using Arithmetic Operators with Dates 3-20
Date Functions 3-21
Using Date Functions 3-22
Practice 3, Part 1 Overview 3-24
Conversion Functions 3-25
Implicit Data-Type Conversion 3-26
Explicit Data-Type Conversion 3-28
Using the TO_CHAR Function with Dates 3-31
Elements of the Date Format Model 3-32
Using the TO_CHAR Function with Dates 3-36
vi

Using the TO_CHAR Function with Numbers 3-37
Using the TO_NUMBER and TO_DATE Functions
RR Date Format 3-40
Example of RR Date Format 3-41
Nesting Functions 3-42
General Functions 3-44
NVL Function 3-45
Using the NVL Function 3-46
Using the NVL2 Function 3-47
Using the NULLIF Function 3-48
Using the COALESCE Function 3-49
Conditional Expressions 3-51
The CASE Expression 3-52
Using the CASE Expression 3-53
The DECODE Function 3-54
Using the DECODE Function 3-55
Summary 3-57
Practice 3, Part 2 Overview 3-58

4

Displaying Data from Multiple Tables
Objectives 4-2
Obtaining Data from Multiple Tables 4-3
Cartesian Products 4-4
Generating a Cartesian Product 4-5
Types of Joins 4-6
Joining Tables Using Oracle Syntax 4-7
vii

3-39

What Is an Equijoin? 4-8
Retrieving Records with Equijoins 4-9
Additional Search Conditions Using the AND Operator
Qualifying Ambiguous Column Names 4-11
Using Table Aliases 4-12
Joining More than Two Tables 4-13
Nonequijoins 4-14
Retrieving Records with Nonequijoins 4-15
Outer Joins 4-16
Outer Joins Syntax 4-17
Using Outer Joins 4-18
Self Joins 4-19
Joining a Table to Itself 4-20
Practice 4, Part 1 Overview 4-21
Joining Tables Using SQL: 1999 Syntax 4-22
Creating Cross Joins 4-23
Creating Natural Joins 4-24
Retrieving Records with Natural Joins 4-25
Creating Joins with the USING Clause 4-26
Retrieving Records with the USING Clause 4-27
Creating Joins with the ON Clause 4-28
Retrieving Records with the ON Clause 4-29
Creating Three-Way Joins with the ON Clause 4-30
INNER versus OUTER Joins 4-31
LEFT OUTER JOIN 4-32
RIGHT OUTER JOIN 4-33
viii

4-10

FULL OUTER JOIN 4-34
Additional Conditions 4-35
Summary 4-36
Practice 4, Part 2 Overview 4-37

5

Aggregating Data Using Group Functions
Objectives 5-2
What Are Group Functions? 5-3
Types of Group Functions 5-4
Group Functions Syntax 5-5
Using the AVG and SUM Functions 5-6
Using the MIN and MAX Functions 5-7
Using the COUNT Function 5-8
Using the DISTINCT Keyword 5-10
Group Functions and Null Values 5-11
Using the NVL Function with Group Functions 5-12
Creating Groups of Data

5-13

Creating Groups of Data: GROUP BY Clause Syntax 5-14
Using the GROUP BY Clause

5-15

Grouping by More Than One Column 5-17
Using the GROUP BY Clause on Multiple Columns 5-18
Illegal Queries Using Group Functions 5-19
Excluding Group Results 5-21
Excluding Group Results: The HAVING Clause 5-22
Using the HAVING Clause 5-23
Nesting Group Functions 5-25
Summary 5-26
Practice 5 Overview 5-27
ix

6

Subqueries
Objectives 6-2
Using a Subquery to Solve a Problem 6-3
Subquery Syntax 6-4
Using a Subquery 6-5
Guidelines for Using Subqueries 6-6
Types of Subqueries 6-7
Single-Row Subqueries 6-8
Executing Single-Row Subqueries 6-9
Using Group Functions in a Subquery 6-10
The HAVING Clause with Subqueries 6-11
What Is Wrong with This Statement? 6-12
Will This Statement Return Rows? 6-13
Multiple-Row Subqueries 6-14
Using the ANY Operator in Multiple-Row Subqueries 6-15
Using the ALL Operator in Multiple-Row Subqueries 6-16
Null Values in a Subquery 6-17
Summary 6-18
Practice 6 Overview 6-19

7

Producing Readable Output with iSQL*Plus
Objectives 7-2
Substitution Variables 7-3
Using the & Substitution Variable 7-5
Character and Date Values with Substitution Variables 7-7
Specifying Column Names, Expressions, and Text 7-8
x

Defining Substitution Variables 7-10
DEFINE and UNDEFINE Commands 7-11
Using the DEFINE Command with & Substitution Variable 7-12
Using the VERIFY Command 7-14
Customizing the iSQL*Plus Environment 7-15
SET Command Variables 7-16
iSQL*Plus Format Commands 7-17
The COLUMN Command 7-18
Using the COLUMN Command 7-19
COLUMN Format Models 7-20
Using the BREAK Command 7-21
Using the TTITLE and BTITLE Commands 7-22
Creating a Script File to Run a Report 7-23
Sample Report 7-25
Summary 7-26
Practice 7 Overview 7-27

8

Manipulating Data
Objectives 8-2
Data Manipulation Language 8-3
Adding a New Row to a Table 8-4
The INSERT Statement Syntax 8-5
Inserting New Rows 8-6
Inserting Rows with Null Values 8-7
Inserting Special Values 8-8
Inserting Specific Date Values 8-9
xi

Creating a Script

8-10

Copying Rows from Another Table 8-11
Changing Data in a Table 8-12
The UPDATE Statement Syntax 8-13
Updating Rows in a Table 8-14
Updating Two Columns with a Subquery 8-15
Updating Rows Based on Another Table 8-16
Updating Rows: Integrity Constraint Error 8-17
Removing a Row from a Table

8-18

The DELETE Statement 8-19
Deleting Rows from a Table 8-20
Deleting Rows Based on Another Table 8-21
Deleting Rows: Integrity Constraint Error 8-22
Using a Subquery in an INSERT Statement 8-23
Using the WITH CHECK OPTION Keyword on DML Statements 8-25
Overview of the Explict Default Feature 8-26
Using Explicit Default Values 8-27
The MERGE Statement 8-28
MERGE Statement Syntax 8-29
Merging Rows 8-30
Database Transactions 8-32
Advantages of COMMIT and ROLLBACK Statements 8-34
Controlling Transactions 8-35
Rolling Back Changes to a Marker 8-36
Implicit Transaction Processing 8-37
State of the Data Before COMMIT or ROLLBACK 8-38
State of the Data After COMMIT 8-39
xii

Committing Data 8-40
State of the Data After ROLLBACK 8-41
Statement-Level Rollback 8-42
Read Consistency 8-43
Implementation of Read Consistency 8-44
Locking 8-45
Implicit Locking 8-46
Summary 8-47
Practice 8 Overview 8-48

9

Creating and Managing Tables
Objectives 9-2
Database Objects 9-3
Naming Rules 9-4
The CREATE TABLE Statement 9-5
Referencing Another User’s Tables 9-6
The DEFAULT Option 9-7
Creating Tables 9-8
Tables in the Oracle Database 9-9
Querying the Data Dictionary 9-10
Data Types 9-11
Datetime Data Types 9-13
TIMESTAMP WITH TIME ZONE Data Type 9-15
TIMESTAMP WITH LOCAL TIME Data Type
INTERVAL YEAR TO MONTH Data Type

9-16

9-17

Creating a Table by Using a Subquery Syntax 9 -18
xiii

Creating a Table by Using a Subquery 9-19
The ALTER TABLE Statement 9-20
Adding a Column 9-22
Modifying a Column 9-24
Dropping a Column 9-25
The SET UNUSED Option 9-26
Dropping a Table 9-27
Changing the Name of an Object 9-28
Truncating a Table 9-29
Adding Comments to a Table 9-30
Summary 9-31
Practice 9 Overview 9-32

10

Including Constraints
Objectives 10-2
What Are Constraints? 10-3
Constraint Guidelines 10-4
Defining Constraints 10-5
The NOT NULL Constraint 10-7
The UNIQUE Constraint 10-9
The PRIMARY KEY Constraint 10-11
The FOREIGN KEY Constraint 10-13
FOREIGN KEY Constraint Keywords 10-15
The CHECK Constraint 10-16
Adding a Constraint Syntax 10-17
Adding a Constraint 10-18
Dropping a Constraint 10-19
xiv

Disabling Constraints 10-20
Enabling Constraints 10-21
Cascading Constraints 10-22
Viewing Constraints 10-24
Viewing the Columns Associated with Constraints 10-25
Summary 10-26
Practice 10 Overview 10-27

11 Creating Views
Objectives 11-2
Database Objects 11-3
What Is a View? 11-4
Why Use Views? 11-5
Simple Views and Complex Views 11-6
Creating a View 11-7
Retrieving Data from a View 11-10
Querying a View 11-11
Modifying a View 11-12
Creating a Complex View 11-13
Rules for Performing DML Operations on a View 11-14
Using the WITH CHECK OPTION Clause 11-17
Denying DML Operations 11-18
Removing a View 11-20
Inline Views 11-21
Top-n Analysis 11-22
Performing Top-n Analysis 11-23
xv

Example of Top-n Analysis 11-24
Summary 11-25
Practice 11 Overview 11-26

12 Other Database Objects
Objectives 12-2
Database Objects 12-3
What Is a Sequence? 12-4
The CREATE SEQUENCE Statement Syntax 12-5
Creating a Sequence 12-6
Confirming Sequences 12-7
NEXTVAL and CURRVAL Pseudocolumns 12-8
Using a Sequence 12-10
Modifying a Sequence 12-12
Guidelines for Modifying a Sequence 12-13
Removing a Sequence 12-14
What Is an Index? 12-15
How Are Indexes Created? 12-16
Creating an Index 12-17
When to Create an Index 12-18
When Not to Create an Index 12-19
Confirming Indexes 12-20
Function-Based Indexes 12-21
Removing an Index 12-22
Synonyms 12-23

xvi

Creating and Removing Synonyms 12-24
Summary 12-25
Practice 12 Overview 12-26

13 Controlling User Access
Objectives 13-2
Controlling User Access 13-3
Privileges 13-4
System Privileges 13-5
Creating Users 13-6
User System Privileges 13-7
Granting System Privileges 13-8
What Is a Role? 13-9
Creating and Granting Privileges to a Role 13-10
Changing Your Password 13-11
Object Privileges 13-12
Granting Object Privileges 13-14
Using the WITH GRANT OPTION and PUBLIC Keywords 13-15
Confirming Privileges Granted

13-16

How to Revoke Object Privileges 13-17
Revoking Object Privileges 13-18
Database Links 13-19
Summary 13-21
Practice 13 Overview 13-22

14 SQL Workshop Workshop Overview
Workshop Overview 14-2
xvii

15 Using SET Operators
Objectives 15-2
The SET Operators 15-3
Tables Used in This Lesson 15-4
The UNION SET Operator 15-7
Using the UNION Operator 15-8
The UNION ALL Operator 15-10
Using the UNION ALL Operator 15-11
The INTERSECT Operator 15-12
Using the INTERSECT Operator 15-13
The MINUS Operator 15-14
SET Operator Guidelines 15-16
The Oracle Server and SET Operators 15-17
Matching the SELECT Statements 15-18
Controlling the Order of Rows 15-20
Summary 15-21
Practice 15 Overview 15-22

16 Oracle 9i Datetime Functions
Objectives 16-2
TIME ZONES 16-3
Oracle 9i Datetime Support 16-4
CURRENT_DATE 16-6
CURRENT_TIMESTAMP 16-7
LOCALTIMESTAMP 16-8
DBTIMEZONE and SESSIONTIMEZONE
xviii

16-9

EXTRACT 16-10
FROM_TZ 16-11
TO_TIMESTAMP and TO_TIMESTAMP_TZ 16-12
TO_YMINTERVAL 16-13
TZ_OFFSET 16-14
Summary 16-16
Practice 16 Overview 16-17

17 Enhancements to the GROUP BY Clause
Objectives 17-2
Review of Group Functions 17-3
Review of the GROUP BY Clause 17-4
Review of the HAVING Clause 17-5
GROUP BY with ROLLUP and CUBE Operators
ROLLUP Operator

17-7

ROLLUP Operator Example
CUBE Operator

17-8

17-9

CUBE Operator: Example
GROUPING Function

17-10

17-11

GROUPING Function: Example 17-12
GROUPING SETS

17-13

GROUPING SETS: Example

17-15

Composite Columns 17-17
Composite Columns: Example

17-19

Concatenated Groupings 17-21

xix

17-6

Concatenated Groupings Example 17-22
Summary 17-23
Practice 17 Overview 17-24

18 Advanced Subqueries
Objectives 18-2
What Is a Subquery? 18-3
Subqueries 18-4
Using a Subquery 18-5
Multiple-Column Subqueries 18-6
Column Comparisons 18-7
Pairwise Comparison Subquery 18-8
Nonpairwise Comparison Subquery 18-9
Using a Subquery in the FROM Clause 18-10
Scalar Subquery Expressions 18-11
Correlated Subqueries 18-14
Using Correlated Subqueries 18-16
Using the EXISTS Operator 18-18
Using the NOT EXISTS Operator 18-20
Correlated UPDATE 18-21
Correlated DELETE 18-24
The WITH Clause 18-26
WITH Clause: Example

18-27

Summary 18-29
Practice 18 Overview 18-31

xx

19 Hierarchical Retrieval
Objectives 19-2
Sample Data from the EMPLOYEES Table 19-3
Natural Tree Structure 19-4
Hierarchical Queries 19-5
Walking the Tree 19-6
Walking the Tree: From the Bottom Up

19-8

Walking the Tree: From the Top Down

19-9

Ranking Rows with the LEVEL Pseudocolumn 19-10
Formatting Hierarchical Reports Using LEVEL and LPAD 19-11
Pruning Branches 19-13
Summary 19-14
Practice 19 Overview 19-15

20 Oracle 9i Extensions to DML and DDL Statements
Objectives 20-2
Review of the INSERT Statement 20-3
Review of the UPDATE Statement 20-4
Overview of Multitable INSERT Statements 20-5
Types of Multitable INSERT Statements 20-7
Multitable INSERT Statements 20-8
Unconditional INSERT ALL 20-10
Conditional INSERT ALL 20-11
Conditional FIRST INSERT 20-13
Pivoting INSERT 20-15
External Tables 20-18
xxi

Creating an External Table 20-19
Example of Creating an External Table 20-20
Querying External Tables 20-23
CREATE INDEX with CREATE TABLE Statement 20-24
Summary 20-25
Practice 20 Overview 20-26

A Practice Solutions
B Table Descriptions and Data
C Using SQL* Plus
D Writing Advanced Scripts
E Oracle Architectural Components

Index
Additional Practices
Additional Practice Solutions
Table and Descriptions

xxii

Creating Views

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this lesson, you should be able
to do the following:

•
•
•
•

Describe a view

•
•

Create and use an inline view

11-2

Create, alter the definition of, and drop a view
Retrieve data through a view
Insert, update, and delete data through
a view
Perform top-n analysis

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this lesson, you learn to create and use views. You also learn to query the relevant data dictionary object
to retrieve information about views. Finally, you learn to create and use inline views, and perform top-n
analysis using inline views.

Introduction to Oracle9i: SQL 11-2

Database Objects

11-3

Object

Description

Table

Basic unit of storage; composed of rows
and columns

View

Logically represents subsets of data from
one or more tables

Sequence

Generates primary key values

Index

Improves the performance of some queries

Synonym

Alternative name for an object

Copyright © Oracle Corporation, 2001. All rights reserved.

Introduction to Oracle9i: SQL 11-3

What Is a View?
EMPLOYEES Table

EMPVU80 View

11-4

Copyright © Oracle Corporation, 2001. All rights reserved.

What Is a View?
You can present logical subsets or combinations of data by creating views of tables. A view is a logical
table based on a table or another view. A view contains no data of its own but is like a window through
which data from tables can be viewed or changed. The tables on which a view is based are called base
tables. The view is stored as a SELECT statement in the data dictionary.

Introduction to Oracle9i: SQL 11-4

Why Use Views?
•
•
•
•

To restrict data access
To make complex queries easy
To provide data independence
To present different views of the same data

11-5

Copyright © Oracle Corporation, 2001. All rights reserved.

Advantages of Views
•

Views restrict access to the data because the view can display selective columns from the table.

•

Views can be used to make simple queries to retrieve the results of complicated queries. For
example, views can be used to query information from multiple tables without the user knowing how
to write a join statement.

•

Views provide data independence for ad hoc users and application programs. One view can be used
to retrieve data from several tables.

•

Views provide groups of users access to data according to their particular criteria.

For more information, see Oracle9i SQL Reference, “CREATE VIEW.”

Introduction to Oracle9i: SQL 11-5

Simple Views
and Complex Views
Feature

Simple Views

Complex Views

Number of tables

One

One or more

Contain functions

No

Yes

Contain groups of data

No

Yes

DML operations
through a view

Yes

Not always

Copyright © Oracle Corporation, 2001. All rights reserved.

11-6

Simple Views versus Complex Views
There are two classifications for views: simple and complex. The basic difference is related to the DML
(INSERT, UPDATE, and DELETE) operations.
•

•

A simple view is one that:
–

Derives data from only one table

–

Contains no functions or groups of data

–

Can perform DML operations through the view

A complex view is one that:
–

Derives data from many tables

–

Contains functions or groups of data

–

Does not always allow DML operations through the view

Introduction to Oracle9i: SQL 11-6

Creating a View
•

You embed a subquery within the CREATE VIEW
statement.

CREATE [OR REPLACE] [FORCE|NOFORCE] VIEW view
[(alias[, alias]...)]
AS subquery
[WITH CHECK OPTION [CONSTRAINT constraint]]
[WITH READ ONLY [CONSTRAINT constraint]];

•

The subquery can contain complex SELECT
syntax.

11-7

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a View
You can create a view by embedding a subquery within the CREATE VIEW statement.
In the syntax:
OR REPLACE

re-creates the view if it already exists

FORCE

creates the view regardless of whether or not the base tables exist

NOFORCE

creates the view only if the base tables exist (This is the defa ult.)

view

is the name of the view

alias

specifies names for the expressions selected by the view’s query (The
number of aliases must match the number of expressions selected by the
view.)

subquery

is a complete SELECT statement (You can use aliases for the columns
in the SELECT list.)

WITH CHECK OPTION

specifies that only rows accessible to the view can be inserted or
updated

constraint

is the name assigned to the CHECK OPTION constraint

WITH READ ONLY

ensures that no DML operations can be performed on this view

Introduction to Oracle9i: SQL 11-7

Creating a View
•

Create a view, EMPVU80, that contains details of
employees in department 80.

CREATE VIEW empvu80
AS SELECT employee_id, last_name, salary
FROM
employees
WHERE
department_id = 80;
View created.

•

Describe the structure of the view by using the
iSQL*Plus DESCRIBE command.

DESCRIBE empvu80

11-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a View (continued)
The example in the slide creates a view that contains the employee number, last name, and salary for each
employee in department 80.
You can display the structure of the view by using the iSQL*Plus DESCRIBE command.

Guidelines for creating a view:
•

The subquery that defines a view can contain complex SELECT syntax, including joins, groups, and
subqueries.

•

The subquery that defines the view cannot contain an ORDER BY clause. The ORDER BY clause is
specified when you retrieve data from the view.

•

If you do not specify a constraint name for a view created with the WITH CHECK OPTION, the
system assigns a default name in the format SYS_Cn.

•

You can use the OR REPLACE option to change the definition of the view without dropping and recreating it or regranting object privileges previously granted on it.

Introduction to Oracle9i: SQL 11-8

Creating a View
•

Create a view by using column aliases in the
subquery.

CREATE VIEW salvu50
AS SELECT employee_id ID_NUMBER, last_name NAME,
salary*12 ANN_SALARY
FROM
employees
WHERE
department_id = 50;
View created.

•

11-9

Select the columns from this view by the given
alias names.

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a View (continued)
You can control the column names by including column aliases within the subquery.
The example in the slide creates a view containing the employee number (EMPLOYEE_ID) with the alias
ID_NUMBER, name (LAST_NAME) with the alias NAME, and annual salary (SALARY) with the alias
ANN_SALARY for every employee in department 50.
As an alternative, you can use an alias after the CREATE statement and prior to the SELECT subquery. The
number of aliases listed must match the number of expressions selected in the subquery.
CREATE VIEW
salvu50 (ID_NUMBER, NAME, ANN_SALARY)
AS SELECT employee_id, last_name, salary*12
FROM
employees
WHERE
department_id = 50;
View created.

Introduction to Oracle9i: SQL 11-9

Retrieving Data from a View

SELECT *
FROM salvu50;

11-10

Copyright © Oracle Corporation, 2001. All rights reserved.

Retrieving Data from a View
You can retrieve data from a view as you would from any table. You can display either the contents of the
entire view or just specific rows and columns.

Introduction to Oracle9i: SQL 11-10

Querying a View

Oracle Server
iSQL*Plus
USER_VIEWS
SELECT
FROM

*

EMPVU80
empvu80;

SELECT employee_id,
last_name, salary
FROM
employees
WHERE department_id=80;

EMPLOYEES

11-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Views in the Data Dictionary
Once your view has been created, you can query the data dictionary view called USER_VIEWS to see the
name of the view and the view definition. The text of the SELECT statement that constitutes your view is
stored in a LONG column.
Data Access Using Views
When you access data using a view, the Oracle Server performs the following operations:
1. It retrieves the view definition from the data dictionary table USER_VIEWS.
2. It checks access privileges for the view base table.
3. It converts the view query into an equivalent operation on the underlying base table or tables. In
other words, data is retrieved from, or an update is made to, the base tables.

Introduction to Oracle9i: SQL 11-11

Modifying a View
•

Modify the EMPVU80 view by using CREATE OR
REPLACE VIEW clause. Add an alias for each
column name.

CREATE OR REPLACE VIEW empvu80
(id_number, name, sal, department_id)
AS SELECT employee_id, first_name || ' ' || last_name,
salary, department_id
FROM
employees
WHERE
department_id = 80;
View created.

•

11-12

Column aliases in the CREATE VIEW clause are
listed in the same order as the columns in the
subquery.
Copyright © Oracle Corporation, 2001. All rights reserved.

Modifying a View
With the OR REPLACE option, a view can be created even if one exists with this name already, thus
replacing the old version of the view for its owner. This means that the view can be altered without
dropping, re-creating, and regranting object privileges.
Note: When assigning column aliases in the CREATE VIEW clause, remember that the aliases are listed in
the same order as the columns in the subquery.

Introduction to Oracle9i: SQL 11-12

Creating a Complex View

Create a complex view that contains group functions
to display values from two tables.
CREATE VIEW dept_sum_vu
(name, minsal, maxsal, avgsal)
AS SELECT
d.department_name, MIN(e.salary),
MAX(e.salary),AVG(e.salary)
FROM
employees e, departments d
WHERE
e.department_id = d.department_id
GROUP BY d.department_name;
View created.

Copyright © Oracle Corporation, 2001. All rights reserved.

11-13

Creating a Complex View
The example in the slide creates a complex view of department names, minimum salaries, maximum
salaries, and average salaries by department. Note that alternative names have been specified for the view.
This is a requirement if any column of the view is derived from a function or an expression.
You can view the structure of the view by using the iSQL*Plus DESCRIBE command. Display the
contents of the view by issuing a SELECT statement.
SELECT
FROM

*
dept_sum_vu;

Introduction to Oracle9i: SQL 11-13

Rules for Performing
DML Operations on a View
•
•

You can perform DML operations on simple views.
You cannot remove a row if the view contains the
following:
– Group functions
– A GROUP BY clause
– The DISTINCT keyword
– The pseudocolumn ROWNUM keyword

11-14

Copyright © Oracle Corporation, 2001. All rights reserved.

Performing DML Operations on a View
You can perform DML operations on data through a view if those operations follow certain rules.
You can remove a row from a view unless it contains any of the following:
•

Group functions

•

A GROUP BY clause

•

The DISTINCT keyword

•

The pseudocolumn ROWNUM keyword

Introduction to Oracle9i: SQL 11-14

Rules for Performing
DML Operations on a View
You cannot modify data in a view if it contains:
– Group functions
– A GROUP BY clause
– The DISTINCT keyword
– The pseudocolumn ROWNUM keyword
– Columns defined by expressions

11-15

Copyright © Oracle Corporation, 2001. All rights reserved.

Performing DML Operations on a View (continued)
You can modify data through a view unless it contains any of the conditions mentioned in the previous slide
or columns defined by expressions: for example, SALARY * 12.

Introduction to Oracle9i: SQL 11-15

Rules for Performing
DML Operations on a View
You cannot add data through a view if the view
includes:
– Group functions
– A GROUP BY clause
– The DISTINCT keyword
– The pseudocolumn ROWNUM keyword
– Columns defined by expressions
– NOT NULL columns in the base tables that are not
selected by the view

11-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Performing DML Operations on a View (continued)
You can add data through a view unless it contains any of the items listed in the slide or ther e are NOT
NULL columns, without default values, in the base table that are not selected by the view. All required
values must be present in the view. Remember that you are adding values directly into the underlying table
through the view.
For more information, see 0racle9i SQL Reference, “CREATE VIEW.”

Introduction to Oracle9i: SQL 11-16

Using the WITH CHECK OPTION Clause

•

You can ensure that DML operations performed on
the view stay within the domain of the view by
using the WITH CHECK OPTION clause.

CREATE OR REPLACE VIEW empvu20
AS SELECT
*
FROM
employees
WHERE
department_id = 20
WITH CHECK OPTION CONSTRAINT empvu20_ck;
View created.

•

11-17

Any attempt to change the department number for
any row in the view fails because it violates the
WITH CHECK OPTION constraint.

Copyright © Oracle Corporation, 2001. All rights reserved.

Using the WITH CHECK OPTION Clause
It is possible to perform referential integrity checks through views. You can also enforce constraints at the
database level. The view can be used to protect data integrity, but the use is very limited.
The WITH CHECK OPTION clause specifies that INSERTs and UPDATEs performed through the view
cannot create rows which the view cannot select, and therefore it allows integrity constraints and data
validation checks to be enforced on data being inserted or updated.
If there is an attempt to perform DML operations on rows that the view has not selected, an error is
displayed, with the constraint name if that has been specified.
UPDATE empvu20
SET
department_id = 10
WHERE employee_id = 201;
UPDATE empvu20
*
ERROR at line 1:
ORA-01402: view WITH CHECK OPTION where -clause violation
Note: No rows are updated because if the department number were to change to 10, the view would no
longer be able to see that employee. Therefore, with the WITH CHECK OPTION clause, the view can see
only employees in department 20 and does not allow the department number for those employees to be
changed through the view.

Introduction to Oracle9i: SQL 11-17

Denying DML Operations

11-18

•

You can ensure that no DML operations occur by
adding the WITH READ ONLY option to your view
definition.

•

Any attempt to perform a DML on any row in the
view results in an Oracle server error.

Copyright © Oracle Corporation, 2001. All rights reserved.

Denying DML Operations
You can ensure that no DML operations occur on your view by creating it with the WITH READ ONLY
option. The example in the slide modifies the EMPVU10 view to prevent any DML operations on the view.

Introduction to Oracle9i: SQL 11-18

Denying DML Operations
CREATE OR REPLACE VIEW empvu10
(employee_number, employee_name, job_title)
AS SELECT
employee_id, last_name, job_id
FROM
employees
WHERE
department_id = 10
WITH READ ONLY;
View created.

11-19

Copyright © Oracle Corporation, 2001. All rights reserved.

Denying DML Operations
Any attempts to remove a row from a view with a read-only constraint results in an error.
DELETE FROM empvu10
WHERE employee_number = 200;
DELETE FROM empvu10
*
ERROR at line 1:
ORA-01752: cannot delete from view without exactly one key preserved table
Any attempts to insert a row or modify a row using the view with a read-only constraint results in the
following Oracle Server error:
01733: virtual column not allowed here.

Introduction to Oracle9i: SQL 11-19

Removing a View

You can remove a view without losing data because a
view is based on underlying tables in the database.

DROP VIEW view;

DROP VIEW empvu80;
View dropped.

11-20

Copyright © Oracle Corporation, 2001. All rights reserved.

Removing a View
You use the DROP VIEW statement to remove a view. The statement removes the view definition from the
database. Dropping views has no effect on the tables on which the view was based. Views or other
applications based on deleted views become invalid. Only the creator or a user with the DROP ANY VIEW
privilege can remove a view.
In the syntax:
view

is the name of the view

Introduction to Oracle9i: SQL 11-20

Inline Views
•
•
•

11-21

An inline view is a subquery with an alias (or
correlation name) that you can use within a SQL
statement.
A named subquery in the FROM clause of the main
query is an example of an inline view.
An inline view is not a schema object.

Copyright © Oracle Corporation, 2001. All rights reserved.

Inline Views
An inline view is created by placing a subquery in the FROM clause and giving that subquery an alias. The
subquery defines a data source that can be referenced in the main query. In the following example, the inline
view b returns the details of all department numbers and the maximum salary for each department from the
EMPLOYEES table. The WHERE a.department_id = b.department_id AND a.salary <
b.maxsal clause of the main query displays employee names, salaries, department numbers, and maximum
salaries for all the employees who earn less than the maximum sa lary in their department.
SELECT
FROM
WHERE
AND

a.last_name, a.salary, a.department_id, b. maxsal
employees a, (SELECT
department_id, max(salary) maxsal
FROM
employees
GROUP BY department_id) b
a.department_id = b.department_id
a.salary < b.maxsal;

Introduction to Oracle9i: SQL 11-21

Top-n Analysis
•

Top-n queries ask for the n largest or smallest
values of a column. For example:
– What are the ten best selling products?
– What are the ten worst selling products ?

•

Both largest values and smallest values sets are
considered top-n queries.

11-22

Copyright © Oracle Corporation, 2001. All rights reserved.

Top-n Analysis
Top-n queries are useful in scenarios where the need is to display only the n top-most or the n bottommost
records from a table based on a condition. This result set can be used for further analysis. For example
using top-n analysis you can perform the following types of queries:
•

The top three earners in the company

•

The four most recent recruits in the company

•

The top two sales representatives who have sold the maximum number of products

•

The top three products that have had the maximum sales in the last six months

Introduction to Oracle9i: SQL 11-22

Performing Top-n Analysis

The high-level structure of a top-n analysis
query is:
SELECT [column_list], ROWNUM
FROM
(SELECT [column_list]
FROM table
ORDER BY Top-N_column)
WHERE ROWNUM <= N;

Copyright © Oracle Corporation, 2001. All rights reserved.

11-23

Performing Top-n Analysis
Top-n queries use a consistent nested query structure with the elements descr ibed below:
•

A subquery or an inline view to generate the sorted list of data. The subquery or the inline view
includes the ORDER BY clause to ensure that the ranking is in the desired order. For results
retrieving the largest values, a DESC parameter is needed.

•

An outer query to limit the number of rows in the final result s et. The outer query includes the
following components:
–

The ROWNUM pseudocolumn, which assigns a sequential value starting with 1 to each of th e
rows returned from the subquery.

–

A WHERE clause, which specifies the n rows to be returned. The outer WHERE clause must
use a < or <= operator.

Introduction to Oracle9i: SQL 11-23

Example of Top-n Analysis

To display the top three earner names and salaries
from the EMPLOYEES table.
SELECT ROWNUM as RANK, last_name, salary
FROM (SELECT last_name,salary FROM employees
ORDER BY salary DESC)
WHERE ROWNUM <= 3;

11-24

Copyright © Oracle Corporation, 2001. All rights reserved.

Example of Top-n Analysis
The example in the slide illustrates how to display the names an d salaries of the top three earners from the
EMPLOYEES table. The subquery returns the details of all employee names and salaries from the
EMPLOYEES table, sorted in the descending order of the salaries. The WHERE ROWNUM < 3 clause of
the main query ensures that only the first three records from this result set are displayed.
Here is another example of top-n analysis that uses an inline view. The example below uses the inline vie w
E to display the four most senior employees in the company.
SELECT ROWNUM as SENIOR,E.last_name, E.hire_date
FROM (SELECT last_name,hire_date FROM employees
ORDER BY hire_date)E
WHERE rownum <= 4;

Introduction to Oracle9i: SQL 11-24

Summary
In this lesson you should have learned that a view is
derived from data in other tables or other views and
provides the following advantages:
• Restricts database access
• Simplifies queries
• Provides data independence
• Provides multiple views of the same data
• Can be dropped without removing the underlying
data

11-25

Copyright © Oracle Corporation, 2001. All rights reserved.

What Is a View?
A view is based on a table or another view and acts as a window through which data on tables can be
viewed or changed. A view does not contain data. The definition of the view is stored in the data
dictionary. You can see the definition of the view in the USER_VIEWS data dictionary table.
Advantages of Views
•

Restrict database access

•

Simplify queries

•

Provide data independence

•

Provide multiple views of the same data

•

Can be removed without affecting the underlying data

View Options
•

Can be a simple view, based on one table

•

Can be a complex view based on more than one table or can contain groups of functions

•

Can replace other views with the same name

•

Can contain a check constraint

•

Can be read-only

Introduction to Oracle9i: SQL 11-25

Practice 11 Overview

This practice covers the following topics:

•
•
•
•
•
•

Creating a simple view
Creating a complex view
Creating a view with a check constraint
Attempting to modify data in the view
Displaying view definitions
Removing views

11-26

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 11 Overview
In this practice, you create simple and complex views and attempt to perform DML statements on the
views.

Introduction to Oracle9i: SQL 11-26

Practice 11
1. Create a view called EMPLOYEES_VU based on the employee numbers, employee names, and
department numbers from the EMPLOYEES table. Change the heading for the employee name to
EMPLOYEE.
2. Display the contents of the EMPLOYEES_VU view.

3. Select the view name and text from the USER_VIEWS data dictionary view.
Note: Another view already exists. The EMP_DETAILS_VIEW was created as part of your schema.
Note: To see more contents of a LONG column, use the iSQL*Plus command SET LONG n, where n is
the value of the number of characters of the LONG column that you want to see.

4. Using your EMPLOYEES_VU view, enter a query to display all employee names and department
numbers.

Introduction to Oracle9i: SQL 11-27

Practice 11 (continued)
5. Create a view named DEPT50 that contains the employee numbers, employee last names, and
department numbers for all employees in department 50. Label the view columns
EMPNO, EMPLOYEE, and DEPTNO. Do not allow an employee to be reassigned to another
department through the view.
6. Display the structure and contents of the DEPT50 view.

7. Attempt to reassign Matos to department 80.
If you have time, complete the following exercise:
8. Create a view called SALARY_VU based on the employee last names, department names, salaries,
and salary grades for all employees. Use the EMPLOYEES, DEPARTMENTS, and JOB_GRADES
tables. Label the columns Employee, Department, Salary, and Grade, respectively.

Introduction to Oracle9i: SQL 11-28

Other Database Objects

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this lesson, you should be able to
do the following:

•
•
•

12-2

Create, maintain, and use sequences
Create and maintain indexes
Create private and public synonyms

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this lesson, you learn how to create and maintain some of the other commonly used database objects.
These objects include sequences, indexes, and synonyms.

Introduction to Oracle9i: SQL 12-2

Database Objects
Object

Description

Table

Basic unit of storage; composed of rows
and columns

View

Logically represents subsets of data from
one or more tables

Sequence

Generates primary key values

Index

Improves the performance of some queries

Synonym

Alternative name for an object

12-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Database Objects
Many applications require the use of unique numbers as primary key values. You can either build code into
the application to handle this requirement or use a sequence to generate unique numbers.
If you want to improve the performance of some queries, you should consider creating an index. You can
also use indexes to enforce uniqueness on a column or a collection of columns.
You can provide alternative names for objects by using synonyms.

Introduction to Oracle9i: SQL 12-3

What Is a Sequence?

A sequence:

•
•
•
•
•

Automatically generates unique numbers
Is a sharable object
Is typically used to create a primary key value
Replaces application code
Speeds up the efficiency of accessing sequence
values when cached in memory

12-4

Copyright © Oracle Corporation, 2001. All rights reserved.

What Is a Sequence?
A sequence is a user created database object that can be shared by multiple users to generate unique
integers.
A typical usage for sequences is to create a primary key value, which must be unique for each row. The
sequence is generated and incremented (or decremented) by an internal Oracle routine. This can be a timesaving object because it can reduce the amount of application code needed to write a sequence-generating
routine.
Sequence numbers are stored and generated independently of tables. Therefore, the same sequence can be
used for multiple tables.

Introduction to Oracle9i: SQL 12-4

The CREATE SEQUENCE Statement Syntax

Define a sequence to generate sequential numbers
automatically.
CREATE SEQUENCE sequence
[INCREMENT BY n]
[START WITH n]
[{MAXVALUE n | NOMAXVALUE}]
[{MINVALUE n | NOMINVALUE}]
[{CYCLE | NOCYCLE}]
[{CACHE n | NOCACHE}];

12-5

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a Sequence
Automatically generate sequential numbers by using the CREATE SEQUENCE statement.
In the syntax:
sequence

is the name of the sequence generator

INCREMENT BY n

specifies the interval between sequence numbers where n is an
integer (If this clause is omitted, the sequence increments by 1.)

START WITH n

specifies the first sequence number to be generated (If this clause is
omitted, the sequence starts with 1.)

MAXVALUE n

specifies the maximum value the sequence can generate

NOMAXVALUE

specifies a maximum value of 10^27 for an ascending sequence and
–1 for a descending sequence (This is the default option.)

MINVALUE n

specifies the minimum sequence value

NOMINVALUE

specifies a minimum value of 1 for an ascending sequence and –
(10^26) for a descending sequence (This is the default option.)

CYCLE | NOCYCLE

specifies whether the sequence continues to generate values afte r
reaching its maximum or minimum value (NOCYCLE is the default option.)

CACHE n | NOCACHE

specifies how many values the Oracle Server preallocates and
keep in memory (By default, the Oracle Server caches 20 values.)

Introduction to Oracle9i: SQL 12-5

Creating a Sequence
•
•

Create a sequence named DEPT_DEPTID_SEQ to
be used for the primary key of the DEPARTMENTS
table.
Do not use the CYCLE option.

CREATE SEQUENCE dept_deptid_seq
INCREMENT BY 10
START WITH 120
MAXVALUE 9999
NOCACHE
NOCYCLE;
Sequence created.

12-6

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a Sequence (continued)
The example in the slide creates a sequence named DEPT_DEPTID_SEQ to be used for the
DEPARTMENT_ID column of the DEPARTMENTS table. The sequence starts at 120, does not allow
caching, and does not cycle.
Do not use the CYCLE option if the sequence is used to generate primary key values, unless you have a
reliable mechanism that purges old rows faster than the sequence cycles.
For more information, see Oracle9i SQL Reference, “CREATE SEQUENCE.”
Note: The sequence is not tied to a table. Generally, you should name the sequence after its intended use;
however the sequence can be used anywhere, regardless of its name.

Introduction to Oracle9i: SQL 12-6

Confirming Sequences
•

Verify your sequence values in the
USER_SEQUENCES data dictionary table.

SELECT
FROM

•

sequence_name, min_value, max_value,
increment_by, last_number
user_sequences;

The LAST_NUMBER column displays the next
available sequence number if NOCACHE is
specified.

12-7

Copyright © Oracle Corporation, 2001. All rights reserved.

Confirming Sequences
Once you have created your sequence, it is documented in the data dictionary. Because a sequence is a
database object, you can identify it in the USER_OBJECTS data dictionary table.
You can also confirm the settings of the sequence by selecting from the USER_SEQUENCES data
dictionary view.

Introduction to Oracle9i: SQL 12-7

NEXTVAL and CURRVAL Pseudocolumns
•

NEXTVAL returns the next available sequence
value.
It returns a unique value every time it is referenced,
even for different users.

•
•

CURRVAL obtains the current sequence value.
NEXTVAL must be issued for that sequence before
CURRVAL contains a value.

12-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Using a Sequence
After you create your sequence, it generates sequential numbers for use in your tables. Reference the
sequence values by using the NEXTVAL and CURRVAL pseudocolumns.
NEXTVAL and CURRVAL Pseudocolumns
The NEXTVAL pseudocolumn is used to extract successive sequence numbers from a specified sequence.
You must qualify NEXTVAL with the sequence name. When you reference sequence.NEXTVAL, a new
sequence number is generated and the current sequence number is placed in CURRVAL.
The CURRVAL pseudocolumn is used to refer to a sequence number that the current user has just generated.
NEXTVAL must be used to generate a sequence number in the current user’s session before CURRVAL can
be referenced. You must qualify CURRVAL with the sequence name. When sequence.CURRVAL is
referenced, the last value returned to that user’s process is displayed.

Introduction to Oracle9i: SQL 12-8

Rules for Using NEXTVAL and CURRVAL
You can use NEXTVAL and CURRVAL in the following contexts:
•

The SELECT list of a SELECT statement that is not part of a subquery

•

The SELECT list of a subquery in an INSERT statement

•

The VALUES clause of an INSERT statement

•

The SET clause of an UPDATE statement

You cannot use NEXTVAL and CURRVAL in the following contexts:
•

The SELECT list of a view

•

A SELECT statement with the DISTINCT keyword

•

A SELECT statement with GROUP BY, HAVING, or ORDER BY clauses

•

A subquery in a SELECT, DELETE, or UPDATE statement

•

The DEFAULT expression in a CREATE TABLE or ALTER TABLE statement

For more information, see Oracle9i SQL Reference, “Pseudocolumns” and “CREATE SEQUENCE section.”

Introduction to Oracle9i: SQL 12-9

Using a Sequence
•

Insert a new department named “Support” in
location ID 2500.

INSERT INTO departments(department_id,
department_name, location_id)
VALUES
(dept_deptid_seq.NEXTVAL,
'Support', 2500);
1 row created.

•

View the current value for the DEPT_DEPTID_SEQ
sequence.

SELECT
FROM

12-10

dept_deptid_seq.CURRVAL
dual;

Copyright © Oracle Corporation, 2001. All rights reserved.

Using a Sequence
The example in the slide inserts a new department in the DEPARTMENTS table. It uses the
DEPT_DEPTID_SEQ sequence for generating a new department number as follows:
SELECT dept_deptid_seq.CURRVAL
FROM
dual;
CURRVAL
--------120
Suppose now you want to hire employees to staff the new department. The INSERT statement to be
executed for all new employees can include the following code:
INSERT INTO employees (employee_id, department_id, ...)
VALUES (employees_seq.NEXTVAL, dept_deptid_seq .CURRVAL, ...);
Note: The preceding example assumes that a sequence called EMPLOYEE_SEQ has already been created
for generating new employee numbers.

Introduction to Oracle9i: SQL 12-10

Using a Sequence
•

Caching sequence values in memory gives faster
access to those values.

•

Gaps in sequence values can occur when:
– A rollback occurs
– The system crashes
– A sequence is used in another table

•

If the sequence was created with NOCACHE, view
the next available value, by querying the
USER_SEQUENCES table.

12-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Caching Sequence Values
Cache sequences in memory to provide faster access to those sequence values. The cache is populated the first
time you refer to the sequence. Each request for the next sequence value is retrieved from the cached
sequence. After the last sequence value is used, the next request for the sequence pulls another cache of
sequences into memory.
Gaps in the Sequence
Although sequence generators issue sequential numbers without ga ps, this action occurs independent of a
commit or rollback. Therefore, if you roll back a statement containing a sequence, the number is lost.
Another event that can cause gaps in the sequence is a system crash. If the sequence caches values in the
memory, then those values are lost if the system crashes.
Because sequences are not tied directly to tables, the same sequence can be used for multiple tables. If you do
so, each table can contain gaps in the sequential numbers.
Viewing the Next Available Sequence Value without Incrementing It
If the sequence was created with NOCACHE, it is possible to view the next available sequence value without
incrementing it by querying the USER_SEQUENCES table.

Introduction to Oracle9i: SQL 12-11

Modifying a Sequence

Change the increment value, maximum value,
minimum value, cycle option, or cache option.

ALTER SEQUENCE dept_deptid_seq
INCREMENT BY 20
MAXVALUE 999999
NOCACHE
NOCYCLE;
Sequence altered.

Copyright © Oracle Corporation, 2001. All rights reserved.

12-12

Altering a Sequence
If you reach the MAXVALUE limit for your sequence, no additional values from the sequence are allocated
and you will receive an error indicating that the sequence exceeds the MAXVALUE. To continue to use the
sequence, you can modify it by using the ALTER SEQUENCE statement.
Syntax
ALTER

SEQUENCE
sequence
[INCREMENT BY n]
[{MAXVALUE n | NOMAXVALUE}]
[{MINVALUE n | NOMINVALUE}]
[{CYCLE | NOCYCLE}]
[{CACHE n | NOCACHE}];

In the syntax:
sequence

is the name of the sequence generator

For more information, see Oracle9i SQL Reference, “ALTER SEQUENCE.”

Introduction to Oracle9i: SQL 12-12

Guidelines for Modifying
a Sequence

12-13

•

You must be the owner or have the ALTER
privilege for the sequence.

•
•

Only future sequence numbers are affected.

•

Some validation is performed.

The sequence must be dropped and
re-created to restart the sequence at a different
number.

Copyright © Oracle Corporation, 2001. All rights reserved.

Guidelines for Modifying Sequences
• You must be the owner or have the ALTER privilege for the sequence in order to modify it.
•

Only future sequence numbers are affected by the ALTER SEQUENCE statement.

•

The START WITH option cannot be changed using ALTER SEQUENCE. The sequence must be
dropped and re-created in order to restart the sequence at a different number.

•

Some validation is performed. For example, a new MAXVALUE that is less than the current sequence
number cannot be imposed.
ALTER SEQUENCE dept_deptid_seq
INCREMENT BY 20
MAXVALUE 90
NOCACHE
NOCYCLE;
ALTER SEQUENCE dept_deptid_seq
*
ERROR at line 1:
ORA-04009: MAXVALUE cannot be made to be less than the current
value

Introduction to Oracle9i: SQL 12-13

Removing a Sequence
•

Remove a sequence from the data dictionary by
using the DROP SEQUENCE statement.

•

Once removed, the sequence can no longer be
referenced.

DROP SEQUENCE dept_deptid_seq;
Sequence dropped.

Copyright © Oracle Corporation, 2001. All rights reserved.

12-14

Removing a Sequence
To remove a sequence from the data dictionary, use the DROP SEQUENCE statement. You must be the
owner of the sequence or have the DROP ANY SEQUENCE privilege to remove it.
Syntax
DROP

SEQUENCE

sequence;

In the syntax:
sequence

is the name of the sequence generator

For more information, see Oracle9i SQL Reference, “DROP SEQUENCE.”

Introduction to Oracle9i: SQL 12-14

What Is an Index?

An index:

12-15

•
•

Is a schema object

•

Can reduce disk I/O by using a rapid path access
method to locate data quickly

•
•

Is independent of the table it indexes

Is used by the Oracle Server to speed up the
retrieval of rows by using a pointer

Is used and maintained automatically by the
Oracle Server

Copyright © Oracle Corporation, 2001. All rights reserved.

Indexes
An Oracle Server index is a schema object that can speed up the retrieval of rows by using a pointer.
Indexes can be created explicitly or automatically. If you do not have an index on the column, then a full
table scan occurs.
An index provides direct and fast access to rows in a table. Its purpose is to reduce the necessity of disk I/O
by using an indexed path to locate data quickly. The index is used and maintained automatically by the
Oracle Server. Once an index is created, no direct activity is required by the user.
Indexes are logically and physically independent of the table they index. This means that they can be
created or dropped at any time and have no effect on the base tables or other indexes.
Note: When you drop a table, corresponding indexes are also dropped.
For more information, see Oracle9i Concepts, “Schema Objects” section, “Indexes” topic.

Introduction to Oracle9i: SQL 12-15

How Are Indexes Created?
•

Automatically: A unique index is created
automatically when you define a PRIMARY KEY or
UNIQUE constraint in a table definition.

•

Manually: Users can create nonunique indexes on
columns to speed up access to the rows.

12-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Types of Indexes
Two types of indexes can be created. One type is a unique index: the Oracle Server automatically creates
this index when you define a column in a table to have a PRIMARY KEY or a UNIQUE key constraint. The
name of the index is the name given to the constraint.
The other type of index is a nonunique index, which a user can create. For example, you can create a
FOREIGN KEY column index for a join in a query to improve retrieval speed.
Note: You can manually create a unique index, but it is recommended that you create a unique constraint,
which implicitly creates a unique index.

Introduction to Oracle9i: SQL 12-16

Creating an Index
•

Create an index on one or more columns.

CREATE INDEX index
ON table (column[, column]...);

•

Improve the speed of query access to the
LAST_NAME column in the EMPLOYEES table.

CREATE INDEX emp_last_name_idx
ON
employees(last_name);
Index created.

12-17

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating an Index
Create an index on one or more columns by issuing the CREATE INDEX statement.
In the syntax:
index

is the name of the index

table

is the name of the table

column

is the name of the column in the table to be indexed

For more information, see Oracle9i SQL Reference, “CREATE INDEX.”

Introduction to Oracle9i: SQL 12-17

When to Create an Index

You should create an index if:

•
•
•

A column contains a wide range of values

•

The table is large and most queries are expected
to retrieve less than 2 to 4% of the rows

A column contains a large number of null values
One or more columns are frequently used together
in a WHERE clause or a join condition

12-18

Copyright © Oracle Corporation, 2001. All rights reserved.

More Is Not Always Better
More indexes on a table does not mean faster queries. Each DML operation that is committed on a table
with indexes means that the indexes must be updated. The more indexes you have associated with a table,
the more effort the Oracle server must make to update all the indexes after a DML operation.
When to Create an Index
Therefore, you should create indexes only if:
•

The column contains a wide range of values

•

The column contains a large number of null values

•

One or more columns are frequently used together in a WHERE clause or join condition

•

The table is large and most queries are expected to retrieve less than 2 to 4% of the rows

Remember that if you want to enforce uniqueness, you should defi ne a unique constraint in the table
definition. Then a unique index is created automatically.

Introduction to Oracle9i: SQL 12-18

When Not to Create an Index

It is usually not worth creating an index if:

12-19

•
•

The table is small

•

Most queries are expected to retrieve more than 2
to 4% of the rows in the table

•
•

The table is updated frequently

The columns are not often used as a condition in
the query

The indexed columns are referenced as part of an
expression

Copyright © Oracle Corporation, 2001. All rights reserved.

Introduction to Oracle9i: SQL 12-19

Confirming Indexes
•
•

The USER_INDEXES data dictionary view contains
the name of the index and its uniqueness.
The USER_IND_COLUMNS view contains the index
name, the table name, and the column name.

SELECT
FROM
WHERE
AND

12-20

ic.index_name, ic.column_name,
ic.column_position col_pos,ix.uniqueness
user_indexes ix, user_ind_columns ic
ic.index_name = ix.index_name
ic.table_name = 'EMPLOYEES';

Copyright © Oracle Corporation, 2001. All rights reserved.

Confirming Indexes
Confirm the existence of indexes from the USER_INDEXES data dictionary view. You can also check the
columns involved in an index by querying the USER_IND_COLUMNS view.
The example on the slide displays all the previously created indexes, with the names of the affected
column, and the index’s uniqueness, on the EMPLOYEES table.

Introduction to Oracle9i: SQL 12-20

Function-Based Indexes
•

A function-based index is an index based on
expressions.

•

The index expression is built from table columns,
constants, SQL functions, and user-defined
functions.

CREATE INDEX upper_dept_name_idx
ON departments(UPPER(department_name));
Index created.
SELECT *
FROM
departments
WHERE UPPER(department_name) = 'SALES';

12-21

Copyright © Oracle Corporation, 2001. All rights reserved.

Function-Based Index
Function-based indexes defined with the UPPER(column_name) or LOWER(column_name)
keywords allow case-insensitive searches. For example, the following index:
CREATE INDEX upper_last_name_idx ON employees (UPPER(last_name));
Facilitates processing queries such as:
SELECT * FROM employees WHERE UPPER(last_name) = 'KING';
To ensure that the Oracle Server uses the index rather than performing a full table scan, be sure that the
value of the function is not null in subsequent queries. For example, the following statement is guaranteed
to use the index, but without the WHERE clause the Oracle Server may perform a full table scan:
SELECT * FROM employees
WHERE UPPER (last_name) IS NOT NULL
ORDER BY UPPER (last_name);
The Oracle Server treats indexes with columns marked DESC as function-based indexes. The columns
marked DESC are sorted in descending order.

Introduction to Oracle9i: SQL 12-21

Removing an Index
•

Remove an index from the data dictionary by
using the DROP INDEX command.

DROP INDEX index;

•

Remove the UPPER_LAST_NAME_IDX index from
the data dictionary.

DROP INDEX upper_last_name_idx;
Index dropped.

•

To drop an index, you must be the owner of the
index or have the DROP ANY INDEX privilege.

12-22

Copyright © Oracle Corporation, 2001. All rights reserved.

Removing an Index
You cannot modify indexes. To change an index, you must drop it and then re-create it. Remove an index
definition from the data dictionary by issuing the DROP INDEX statement. To drop an index, you must be
the owner of the index or have the DROP ANY INDEX privilege.
In the syntax:
index

is the name of the index

Note: If you drop a table, indexes and constraints are automatically dropped, but views and sequences
remain.

Introduction to Oracle9i: SQL 12-22

Synonyms

Simplify access to objects by creating a synonym
(another name for an object). With synonyms, you can:

•
•

Ease referring to a table owned by another user
Shorten lengthy object names

CREATE [PUBLIC] SYNONYM synonym
FOR
object;

12-23

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a Synonym for an Object
To refer to a table owned by another user, you need to prefix the table name with the name of the user who
created it followed by a period. Creating a synonym eliminates the need to qualify the object name with the
schema and provides you with an alternative name for a table, view, sequence, procedure, or other objects.
This method can be especially useful with lengthy object names, such as views.
In the syntax:
PUBLIC

creates a synonym accessible to all users

synonym

is the name of the synonym to be created

object

identifies the object for which the synonym is created

Guidelines
•

The object cannot be contained in a package.

•

A private synonym name must be distinct from all other objects owned by the same user.

For more information, see Oracle9i SQL Reference, “CREATE SYNONYM.”

Introduction to Oracle9i: SQL 12-23

Creating and Removing Synonyms
•

Create a shortened name for the
DEPT_SUM_VU view.

CREATE SYNONYM d_sum
FOR dept_sum_vu;
Synonym Created.

•

Drop a synonym.

DROP SYNONYM d_sum;
Synonym dropped.

12-24

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a Synonym for an Object (continued)
The example in the slide creates a synonym for the DEPT_SUM_VU view for quicker reference.
The database administrator can create a public synonym accessible to all users. The following example creates
a public synonym named DEPT for Alice’s DEPARTMENTS table:
CREATE PUBLIC SYNONYM dept
FOR
alice.departments;
Synonym created.
Removing a Synonym
To drop a synonym, use the DROP SYNONYM statement. Only the database administrator can drop a public
synonym.
DROP PUBLIC SYNONYM
Synonym dropped.

dept;

For more information, see Oracle9i SQL Reference, “DROP SYNONYM.”

Introduction to Oracle9i: SQL 12-24

Summary

In this lesson, you should have learned how to:

•

Generate sequence numbers automatically by
using a sequence generator

•

View sequence information in the
USER_SEQUENCES data dictionary table

•
•

Create indexes to improve query retrieval speed
View index information in the USER_INDEXES
dictionary table

•

Use synonyms to provide alternative names for
objects

12-25

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
In this lesson, you should have learned about some of the other database objects including sequences,
indexes, and views.
Sequences
The sequence generator can be used to automatically generate sequence numbers for rows in tables. This
can save time and can reduce the amount of application code needed.
A sequence is a database object that can be shared with other users. Information about the sequence can be
found in the USER_SEQUENCES table of the data dictionary.
To use a sequence, reference it with either the NEXTVAL or the CURRVAL pseudocolumns.
•

Retrieve the next number in the sequence by referencing sequence.NEXTVAL.

•

Return the current available number by referencing sequence.CURRVAL.

Indexes
Indexes are used to improve query retrieval speed. Users can view the definitions of the indexes in the
USER_INDEXES data dictionary view. An index can be dropped by the creator, or a user with the DROP
ANY INDEX privilege, by using the DROP INDEX statement.
Synonyms
Database administrators can create public synonyms and users can create private synonyms for
convenience, by using the CREATE SYNONYM statement. Synonyms permit short names or alternative
names for objects. Remove synonyms by using the DROP SYNONYM statement.
Introduction to Oracle9i: SQL 12-25

Practice 12 Overview

This practice covers the following topics:

•
•
•
•

Creating sequences

•

Dropping indexes

Using sequences
Creating nonunique indexes
Displaying data dictionary information about
sequences and indexes

12-26

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 12 Overview
In this practice, you create a sequence to be used when populating your table. You also create implicit and
explicit indexes.

Introduction to Oracle9i: SQL 12-26

Practice 12
1. Create a sequence to be used with the primary key column of the DEPT table. The
sequence should start at 200 and have a maximum value of 1000. Have your sequence increment
by ten numbers. Name the sequence DEPT_ID_SEQ.
2. Write a query in a script to display the following information about your sequences: sequence name,
maximum value, increment size, and last number. Name the script lab12_2.sql. Run the statement
in your script.

3. Write a script to insert two rows into the DEPT table. Name your script lab12_3.sql. Be sure to use
the sequence that you created for the ID column. Add two departments named Education and
Administration. Confirm your additions. Run the commands in your script.
4. Create a nonunique index on the foreign key column (DEPT_ID) in the EMP table.
5. Display the indexes and uniqueness that exist in the data dictio nary for the EMP table.
Save the statement into a script named lab12_5.sql.

Introduction to Oracle9i: SQL 12-27

Introduction to Oracle9i: SQL 12-28

Controlling User Access

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this lesson, you should be able to
do the following:

•
•
•
•

13-2

Create users
Create roles to ease setup and maintenance of the
security model
Use the GRANT and REVOKE statements to grant
and revoke object privileges
Create and access database links

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this lesson, you learn how to control database access to specific objects and add new users with different
levels of access privileges.

Introduction to Oracle9i: SQL 13-2

Controlling User Access

Database
Administrator

Username and Password
Privileges
Users

13-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Controlling User Access
In a multiple-user environment, you want to maintain security of the database access and use. With Oracle
server database security, you can do the following:
•

Control database access

•

Give access to specific objects in the database

•

Confirm given and received privileges with the Oracle data dictionary

•

Create synonyms for database objects

Database security can be classified into two categories: system security and data security. System security
covers access and use of the database at the system level, such as the username and password, the disk
space allocated to users, and the system operations that users can perform. Database security covers access
and use of the database objects and the actions that those users can have on the objects.

Introduction to Oracle9i: SQL 13-3

Privileges
•

Database security:
– System security
– Data security

•
•

System privileges: Gaining access to the database

•

Schemas: Collections of objects, such as tables,
views, and sequences

13-4

Object privileges: Manipulating the content of the
database objects

Copyright © Oracle Corporation, 2001. All rights reserved.

Privileges
Privileges are the right to execute particular SQL statements. The database administrator (DBA) is a highlevel user with the ability to grant users access to the database and its objects. The users require system
privileges to gain access to the database and object privileges to manipulate the content of the objects in the
database. Users can also be given the privilege to grant additional privileges to other users or to roles,
which are named groups of related privileges.
Schemas
A schema is a collection of objects, such as tables, views, and sequences. The schema is owned by a
database user and has the same name as that user.
For more information, see Oracle9i Application Developer’s Guide - Fundamentals, “Establishing a
Security Policy,” and Oracle9i Concepts, “Database Security.”

Introduction to Oracle9i: SQL 13-4

System Privileges
•
•

More than 100 privileges are available.
The database administrator has high-level system
privileges for tasks such as:
– Creating new users
– Removing users
– Removing tables
– Backing up tables

13-5

Copyright © Oracle Corporation, 2001. All rights reserved.

System Privileges
More than 100 distinct system privileges are available for users and roles. System privileges typically are
provided by the database administrator.
Typical DBA Privileges

System Privilege

Operations Authorized

CREATE USER

Grantee can create other Oracle users (a privilege required
for a DBA role).

DROP USER

Grantee can drop another user.

DROP ANY TABLE

Grantee can drop a table in any schema.

BACKUP ANY TABLE

Grantee can back up any table in any schema with the
export utility.
Grantee can query tables, views, or snapshots in any
schema.
Grantee can create tables in any schema.

SELECT ANY TABLE
CREATE ANY TABLE

Introduction to Oracle9i: SQL 13-5

Creating Users

The DBA creates users by using the CREATE USER
statement.
CREATE USER user
IDENTIFIED BY
password;

CREATE USER scott
IDENTIFIED BY
tiger;
User created.

13-6

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a User
The DBA creates the user by executing the CREATE USER statement. The user does not have any
privileges at this point. The DBA can then grant privileges to that user. These privileges determine what the
user can do at the database level.
The slide gives the abridged syntax for creating a user.
In the syntax:
user

is the name of the user to be created

password

specifies that the user must log in with this password

For more information, see Oracle9i SQL Reference, “GRANT” and “CREATE USER.”

Introduction to Oracle9i: SQL 13-6

User System Privileges
•

Once a user is created, the DBA can grant specific
system privileges to a user.

GRANT privilege [, privilege...]
TO user [, user| role, PUBLIC...];

•

An application developer, for example, may have
the following system privileges:
– CREATE SESSION
– CREATE TABLE
– CREATE SEQUENCE
– CREATE VIEW
– CREATE PROCEDURE

13-7

Copyright © Oracle Corporation, 2001. All rights reserved.

Typical User Privileges
Now that the DBA has created a user, the DBA can assign privileges to that user.

System Privilege

Operations Authorized

CREATE SESSION

Connect to the database

CREATE TABLE

Create tables in the user’s schema

CREATE SEQUENCE

Create a sequence in the user’s schema

CREATE VIEW

Create a view in the user’s schema

CREATE PROCEDURE

Create a stored procedure, function, or package in the user’s
schema

In the syntax:
privilege

is the system privilege to be granted

is the name of the user, the name of the role, or PUBLIC designates
that every user is granted the privilege
Note: Current system privileges can be found in the dictionary view SESSION_PRIVS .
user |role|PUBLIC

Introduction to Oracle9i: SQL 13-7

Granting System Privileges

The DBA can grant a user specific system privileges.
GRANT

create session, create table,
create sequence, create view
TO
scott;
Grant succeeded.

13-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Granting System Privileges
The DBA uses the GRANT statement to allocate system privileges to the user. Once the user has been
granted the privileges, the user can immediately use those privileges.
In the example in the slide, user Scott has been assigned the privileges to create sessions, tables, sequences,
and views.

Introduction to Oracle9i: SQL 13-8

What Is a Role?

Users

Manager

Privileges
Allocating privileges
without a role

Allocating privileges
with a role

Copyright © Oracle Corporation, 2001. All rights reserved.

13-9

What Is a Role?
A role is a named group of related privileges that can be granted to the user. This method makes it easier to
revoke and maintain privileges.
A user can have access to several roles, and several users can be assigned the same role. Roles are typically
created for a database application.
Creating and Assigning a Role
First, the DBA must create the role. Then the DBA can assign privileges to the role and users to the role.
Syntax
CREATE

ROLE

role;

In the syntax:
role

is the name of the role to be created

Now that the role is created, the DBA can use the GRANT statement to assign users to the role as well as
assign privileges to the role.

Introduction to Oracle9i: SQL 13-9

Creating and Granting Privileges to a Role
•

Create a role

CREATE ROLE manager;
Role created.

•

Grant privileges to a role

GRANT create table, create view
TO manager;
Grant succeeded.

•

Grant a role to users

GRANT manager TO DEHAAN, KOCHHAR;
Grant succeeded.

13-10

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating a Role
The example in the slide creates a manager role and then allows managers to create tables and views. It
then grants DeHaan and Kochhar the role of managers. Now DeHaan and Kochhar can create tables and
views.
If users have multiple roles granted to them, they receive all of the privileges assoicated with all of the
roles.

Introduction to Oracle9i: SQL 13-10

Changing Your Password
•

The DBA creates your user account and initializes
your password.

•

You can change your password by using the
ALTER USER statement.

ALTER USER scott
IDENTIFIED BY lion;
User altered.

13-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Changing Your Password
The DBA creates an account and initializes a password for every user. You can change your password by
using the ALTER USER statement.
Syntax
ALTER USER user IDENTIFIED BY password;
In the syntax:
user

is the name of the user

password

specifies the new password

Although this statement can be used to change your password, there are many other options. You must have
the ALTER USER privilege to change any other option.
For more information, see Oracle9i SQL Reference, “ALTER USER.”

Introduction to Oracle9i: SQL 13-11

Object Privileges
Object
Privilege

Table

ALTER

√

DELETE

√

View

Sequence Procedure
√

√
√

EXECUTE

13-12

INDEX

√

INSERT

√

√

REFERENCES

√

√

SELECT

√

√

UPDATE

√

√

√

Copyright © Oracle Corporation, 2001. All rights reserved.

Object Privileges
An object privilege is a privilege or right to perform a particular action on a specific table, view,
sequence, or procedure. Each object has a particular set of grantable privileges. The table in the slide lists
the privileges for various objects. Note that the only privileges that apply to a sequence are SELECT and
ALTER. UPDATE, REFERENCES, and INSERT can be restricted by specifying a subset of updatable
columns. A SELECT privilege can be restricted by creating a view with a subset of columns and granting
the SELECT privilege only on the view. A privilege granted on a synonym is converted to a privilege on
the base table referenced by the synonym.

Introduction to Oracle9i: SQL 13-12

Object Privileges
•
•
•

Object privileges vary from object to object.
An owner has all the privileges on the object.
An owner can give specific privileges on that
owner’s object.

GRANT
ON
TO
[WITH GRANT

13-13

object_priv [(columns)]
object
{user|role|PUBLIC}
OPTION];

Copyright © Oracle Corporation, 2001. All rights reserved.

Granting Object Privileges
Different object privileges are available for different types of schema objects. A user automatically has all
object privileges for schema objects contained in the user’s schema. A user can grant any object privilege
on any schema object that the user owns to any other user or role. If the grant includes WITH GRANT
OPTION, then the grantee can further grant the object privilege to other users; otherwise, the grantee can
use the privilege but cannot grant it to other users.
In the syntax:
object_priv

is an object privilege to be granted

ALL

specifies all object privileges

columns

specifies the column from a table or view on which privileges
are granted

ON object

is the object on which the privileges are granted

TO

identifies to whom the privilege is granted

PUBLIC

grants object privileges to all users

WITH GRANT OPTION

allows the grantee to grant the object privileges to other users
and roles

Introduction to Oracle9i: SQL 13-13

Granting Object Privileges
•

Grant query privileges on the EMPLOYEES table.

GRANT select
ON
employees
TO
sue, rich;
Grant succeeded.

•

Grant privileges to update specific columns to
users and roles.

GRANT update (department_name, location_id)
ON
departments
TO
scott, manager;
Grant succeeded.

Copyright © Oracle Corporation, 2001. All rights reserved.

13-14

Guidelines
•

To grant privileges on an object, the object must be in your own schema, or you must have been granted the
object privileges WITH GRANT OPTION .

•

An object owner can grant any object privilege on the object to any other user or role of the database.

• The owner of an object automatically acquires all object privileges on that object.
The first example in the slide grants users Sue and Rich the privilege to query your EMPLOYEES table. The
second example grants UPDATE privileges on specific columns in the DEPARTMENTS table to Scott and to the
manager role.
If Sue or Rich now want to SELECT data from the employees table, the syntax they must use is:
SELECT

*

FROM

scott.employees;

Alternatively, they can create a synonym for the table and SELECT from the synonym:
CREATE SYNONYM emp FOR scott.employees;
SELECT * FROM emp;
Note: DBAs generally allocate system privileges; any user who owns an object can grant object privileges.

Introduction to Oracle9i: SQL 13-14

Using the WITH GRANT OPTION and
PUBLIC Keywords
•

Give a user authority to pass along privileges.

GRANT select, insert
ON
departments
TO
scott
WITH
GRANT OPTION;
Grant succeeded.

•

Allow all users on the system to query data from
Alice’s DEPARTMENTS table.

GRANT select
ON
alice.departments
TO
PUBLIC;
Grant succeeded.
13-15

Copyright © Oracle Corporation, 2001. All rights reserved.

The WITH GRANT OPTION Keyword
A privilege that is granted with the WITH GRANT OPTION clause can be passed on to other users and
roles by the grantee. Object privileges granted with the WITH GRANT OPTION clause are revoked when
the grantor’s privilege is revoked.
The example in the slide gives user Scott access to your DEPARTMENTS table with the privileges to query
the table and add rows to the table. The example also allows Scott to give others these privileges.
The PUBLIC Keyword
An owner of a table can grant access to all users by using the PUBLIC keyword.
The second example allows all users on the system to query data from Alice’s DEPARTMENTS table.

Introduction to Oracle9i: SQL 13-15

Confirming Privileges Granted
Data Dictionary View

Description

ROLE_SYS_PRIVS

System privileges granted to roles

ROLE_TAB_PRIVS

Table privileges granted to roles

USER_ROLE_PRIVS

Roles accessible by the user

USER_TAB_PRIVS_MADE

Object privileges granted on the
user’s objects

USER_TAB_PRIVS_RECD

Object privileges granted to the
user

USER_COL_PRIVS_MADE

Object privileges granted on the
columns of the user’s objects

USER_COL_PRIVS_RECD

Object privileges granted to the
user on specific columns

USER_SYS_PRIVS

Lists system privileges granted to
the user

13-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Confirming Granted Privileges
If you attempt to perform an unauthorized operation (for example, deleting a row from a table for which
you do not have the DELETE privilege) the Oracle Server does not permit the operation to take place.
If you receive the Oracle Server error message table or view does not exist , you have done
either of the following:
•

Named a table or view that does not exist

•

Attempted to perform an operation on a table or view for which you do not have the appropriate
privilege

You can access the data dictionary to view the privileges that you have. The chart in the slide describes
various data dictionary views.

Introduction to Oracle9i: SQL 13-16

How to Revoke Object Privileges
•
•

You use the REVOKE statement to revoke privileges
granted to other users.
Privileges granted to others through the WITH
GRANT OPTION clause are also revoked.

REVOKE {privilege [, privilege...]|ALL}
ON
object
FROM
{user[, user...]|role|PUBLIC}
[CASCADE CONSTRAINTS];

13-17

Copyright © Oracle Corporation, 2001. All rights reserved.

Revoking Object Privileges
Remove privileges granted to other users by using the REVOKE statement. When you use the REVOKE
statement, the privileges that you specify are revoked from the users you name and from any other users to
whom those privileges were granted through the WITH GRANT OPTION clause.
In the syntax:
CASCADE
CONSTRAINTS

is required to remove any referential integrity constraints made to the
object by means of the REFERENCES privilege

For more information, see Oracle9i SQL Reference, “REVOKE.”

Introduction to Oracle9i: SQL 13-17

Revoking Object Privileges

As user Alice, revoke the SELECT and INSERT
privileges given to user Scott on the DEPARTMENTS
table.
REVOKE select, insert
ON
departments
FROM
scott;
Revoke succeeded.

13-18

Copyright © Oracle Corporation, 2001. All rights reserved.

Revoking Object Privileges (continued)
The example in the slide revokes SELECT and INSERT privileges given to user Scott on the
DEPARTMENTS table.
Note: If a user is granted a privilege with the WITH GRANT OPTION clause, that user can also grant the
privilege with the WITH GRANT OPTION clause, so that a long chain of grantees is possible, but no
circular grants are permitted. If the owner revokes a privilege from a user who granted the privilege to other
users, the revoking cascades to all privileges granted.
For example, if user A grants SELECT privilege on a table to user B including the WITH GRANT OPTION
clause, user B can grant to user C the SELECT privilege with the WITH GRANT OPTION clause as well,
and user C can then grant to user D the SELECT privilege. If user A revokes privilege from user B, then the
privileges granted to users C and D are also revoked.

Introduction to Oracle9i: SQL 13-18

Database Links

A database link connection allows local users to
access data on a remote database.

Local

Remote

fred.EMP
Table
SELECT * FROM
emp@HQ_ACME.COM;

13-19

HQ_ACME.COM
Database

Copyright © Oracle Corporation, 2001. All rights reserved.

Database Links
A database link is a pointer that defines a one-way communication path from an Oracle database server to
another database server. The link pointer is actually defined as an entry in a data dictionary table. To access
the link, you must be connected to the local database that contains the data dictionary entry.
A database link connection is one-way in the sense that a client connected to local database A can use a link
stored in database A to access information in remote database B, but users connected to database B cannot
use the same link to access data in database A. If local users on database B want to access data on database
A, they must define a link that is stored in the data dictionary of database B.
A database link connection gives local users access to data on a remote database. For this connection to
occur, each database in the distributed system must have a unique global database name. The global
database name uniquely identifies a database server in a distributed system.
The great advantage of database links is that they allow users to access another user’s objects in a remote
database so that they are bounded by the privilege set of the object's owner. In other words, a local user can
access a remote database without having to be a user on the remote database.
The example shows a user SCOTT accessing the EMP table on the remote database with the global name
HQ.ACME.COM.
Note: Typically, the DBA is responsible for creating the database link. The dictionary view
USER_DB_LINKS contains information on links to which a user has access.

Introduction to Oracle9i: SQL 13-19

Database Links
•

Create the database link.

CREATE PUBLIC DATABASE LINK hq.acme.com
USING 'sales';
Database link created.

•

Write SQL statements that use the database link.

SELECT *
FROM fred.emp@HQ.ACME.COM;

13-20

Copyright © Oracle Corporation, 2001. All rights reserved.

Using Database Links
The example in the slide creates a database link. The USING clause identifies the service name of a remote
database.
Once the database link is created, you can write SQL statements against the data in the remote site. If a
synonym is set up, you can write SQL statements using the synony m.
For example:
CREATE PUBLIC SYNONYM HQ_EMP FOR emp@HQ.ACME.COM;
Then write a SQL statement that uses the synonym:
SELECT * FROM HQ_EMP;
You cannot grant privileges on remote objects.

Introduction to Oracle9i: SQL 13-20

Summary
In this lesson you should have learned about DCL
statements that control access to the database and
database objects.
Statement
CREATE USER
GRANT
CREATE ROLE
ALTER USER
REVOKE

13-21

Action
Creates a user (usually performed by
a DBA)
Gives other users privileges to
access the your objects
Creates a collection of privileges
(usually performed by a DBA)
Changes a user’s password
Removes privileges on an object from
users

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
DBAs establish initial database security for users by assigning privileges to the users.
•

The DBA creates users who must have a password. The DBA is also responsible for establishing the
initial system privileges for a user.

•

Once the user has created an object, the user can pass along any of the available object privileges to
other users or to all users by using the GRANT statement.

•

A DBA can create roles by using the CREATE ROLE statement to pass along a collection of system
or object privileges to multiple users. Roles make granting and revoking privileges easier to maintain.

•

Users can change their password by using the ALTER USER statement.

•

You can remove privileges from users by using the REVOKE statement.

•

With data dictionary views, users can view the privileges granted to them and those that are granted
on their objects.

•

With database links, you can access data on remote databases. Privileges cannot be granted on remote
objects.

Introduction to Oracle9i: SQL 13-21

Practice 13 Overview

This practice covers the following topics:

•
•

Granting other users privileges to your table

•
•

Creating a synonym

Modifying another user’s table through the
privileges granted to you
Querying the data dictionary views related to
privileges

13-22

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 13 Overview
Team up with other students for this exercise about controlling access to database objects.

Introduction to Oracle9i: SQL 13-22

Practice 13
1. What privilege should a user be given to log on to the Oracle Server? Is this a system or an object
privilege?

_____________________________________________________________________
2. What privilege should a user be given to create tables?

_____________________________________________________________________
3. If you create a table, who can pass along privileges to other users on your table?

_____________________________________________________________________
4. You are the DBA. You are creating many users who require the same system privileges.
What should you use to make your job easier?

_____________________________________________________________________
5. What command do you use to change your password?

_____________________________________________________________________
6. Grant another user access to your DEPARTMENTS table. Have the user grant you query access to his
or her DEPARTMENTS table.
7. Query all the rows in your DEPARTMENTS table.

8. Add a new row to your DEPARTMENTS table. Team 1 should add Education as department
number 500. Team 2 should add Human Resources department number 510. Query the other team’s
table.
9. Create a synonym for the other team’s DEPARTMENTS table.

Introduction to Oracle9i: SQL 13-23

Practice 13 (continued)
10. Query all the rows in the other team’s DEPARTMENTS table by using your synonym.
Team 1 SELECT statement results:

Team 2 SELECT statement results:

Introduction to Oracle9i: SQL 13-24

Practice 13 (continued)
11. Query the USER_TABLES data dictionary to see information about the tables that you own.

12. Query the ALL_TABLES data dictionary view to see information about all the tables that you can
access. Exclude tables that are you own.
Note: Your list may not exactly match the list shown below.

owner

13. Revoke the SELECT privilege on your table from the other team.

Introduction to Oracle9i: SQL 13-25

Introduction to Oracle9i: SQL 13-26

SQL Workshop

Copyright © Oracle Corporation, 2001. All rights reserved.

Workshop Overview

This workshop covers:

•
•
•
•
•
•

Creating tables and sequences
Modifying data in the tables
Modifying table definitions
Creating views
Writing scripts containing SQL and iSQL*Plus
commands
Generating a simple report

14-2

Copyright © Oracle Corporation, 2001. All rights reserved.

Workshop Overview
In this workshop you build a set of database tables for a video application. After you create the tables, you
insert, update, and delete records in a video store database and generate a report. The database contains
only the essential tables.
Note: If you want to build the tables, you can execute the commands in the buildtab.sql script in
iSQL*Plus. If you want to drop the tables, you can execute the commands in dropvid.sql script in
iSQL*Plus. Then you can execute the commands in buildvid.sql script in iSQL*Plus to create and
populate the tables. If you use the buildvid.sql script to build and populate the tables, start with step
6b.

Introduction to Oracle9i: SQL 14-2

Video Application Entity Relationship Diagram

for
RESERVATION
#* reservation date

the subject
of

set up for

TITLE
#* ID
* title
* description
o rating
o category
o release date
available as

a copy

responsible
for
MEMBER
#* ID
* last name
o first name
o address
o city
o phone
* join date

TITLE_COPY
#* ID
* status
the subject of
responsible
for

made against
created
for

Introduction to Oracle9i: SQL 14-3

RENTAL
#* book date
o act ret date
o exp ret date

Practice 14
1. Create the tables based on the following table instance charts. Choose the appropriate data types and
be sure to add integrity constraints.
a. Table name: MEMBER
Column_
Name

MEMBER_
ID

Key
Type
Null/
Unique
Default
Value

PK

Data
Type
Length

NN,U

LAST_
NAME

FIRST_NAM
E

ADDRESS

CITY

PHONE

JOIN
_
DATE

NN

NN

NUMBER

VARCHAR2

VARCHAR2

VARCHAR2

VARCHAR2

VARCHAR2

System
Date
DATE

10

25

25

100

30

15

b. Table name: TITLE
Column_
Name

TITLE_ID

Key
Type
Null/
Unique
Check

PK

Data Type

NUMBER

VARCHAR2

VARCHAR2

Length

10

60

400

NN,U

TITLE

DESCRIPTION

NN

NN

RATING

CATEGORY

G, PG, R,
NC17, NR

VARCHAR2

DRAMA,
COMEDY,
ACTION,
CHILD,
SCIFI,
DOCUMENTARY
VARCHAR2

4

20

Introduction to Oracle9i: SQL 14-4

RELEASE_
DATE

DATE

Practice 14 (continued)
c. Table name: TITLE_COPY
Column
Name
Key
Type
Null/
Unique
Check

FK Ref
Table
FK Ref
Col
Data
Type
Length

COPY_ID

TITLE_ID

PK

PK,FK

NN,U

NN,U

STATUS

NN
AVAILABLE,
DESTROYED,
RENTED,
RESERVED

TITLE
TITLE_ID
NUMBER

NUMBER

VARCHAR2

10

10

15

d. Table name: RENTAL

Column
Name
Key
Type
Default
Value
FK Ref
Table
FK Ref
Col
Data
Type
Length

BOOK_
DATE

MEMBER_
ID

COPY_
ID

PK

PK,FK1

PK,FK2

ACT_RET_ EXP_RET_
DATE
DATE

PK,FK2

System
Date

System Date
+ 2 days
MEMBER

DATE

TITLE_
ID

MEMBER_I
D
NUMBER

TITLE_
COPY
COPY_
ID
NUMBER

10

10

TITLE_
COPY
TITLE_ID
DATE

Introduction to Oracle9i: SQL 14-5

DATE

NUMBER
10

Practice 14 (continued)
e. Table name: RESERVATION

Column
Name
Key
Type
Null/
Unique
FK Ref
Table
FK Ref
Column
Data Type
Length

RES_
DATE

MEMBER_
ID

TITLE_
ID

PK

PK,FK1

PK,FK2

NN,U

NN,U

NN

MEMBER

TITLE

MEMBER_ID

TITLE_ID

NUMBER

NUMBER

10

10

DATE

2. Verify that the tables and constraints were created properly by checking the data dictionary.

18 rows selected.

Introduction to Oracle9i: SQL 14-6

Practice 14 (continued)
3. Create sequences to uniquely identify each row in the MEMBER table and the TITLE table.
a. Member number for the MEMBER table: Start with 101; do not allow caching of the
values. Name the sequence MEMBER_ID_SEQ.
b. Title number for the TITLE table: Start with 92; no caching. Name the sequence
TITLE_ID_SEQ.
c. Verify the existence of the sequences in the data dictionary.

4. Add data to the tables. Create a script for each set of data to add.
a. Add movie titles to the TITLE table. Write a script to enter the movie information.
Save the statements in a script named lab14_4a.sql. Use the sequences to uniquely
identify each title. Enter the release dates in the DD-MON-YYYY format. Remember
that single quotation marks in a character field must be specially handled. Verify your
additions.

Introduction to Oracle9i: SQL 14-7

Practice 14 (continued)

Title

Description

Rating

Category

Release_date

Willie and
Christmas
Too

All of Willie’s friends make
a Christmas list for Santa, but
Willie has yet to add his own
wish list.
Yet another installation of
science fiction history. Can
the heroine save the planet
from the alien life form?
A meteor crashes near a
small American town and
unleashes carnivorous goo in
this classic.
With a little luck and a lot of
ingenuity, a teenager skips
school for a day in New York
A six-year-old has doubts
about Santa Claus, but she
discovers that miracles really
do exist.
After discovering a cache of
drugs, a young couple find
themselves pitted against a
vicious gang.

G

CHILD

05-OCT-1995

R

SCIFI

19-MAY-1995

NR

SCIFI

12-AUG-1995

PG

COMEDY

12-JUL-1995

PG

DRAMA

12-SEP-1995

NR

ACTION

01-JUN-1995

Alien Again

The Glob

My Day Off

Miracles on
Ice

Soda Gang

Introduction to Oracle9i: SQL 14-8

Practice 14 (continued)
b. Add data to the MEMBER table. Place the insert statements in a script named
lab14_4b.sql. Execute commands in the script. Be sure to use the sequence to add the
member numbers.

First_
Name
Carmen

Last_Name
Velasquez

LaDoris

Ngao

Midori

Nagayama

Mark

Address
283 King
Street
5 Modrany

City
Seattle

Phone
206-899-6666

Join_Date
08-MAR-1990

Bratislava

586-355-8882

08-MAR-1990

Sao Paolo

254-852-5764

17-JUN-1991

Lagos

63-559-7777

07-APR-1990

Audry

Quick-toSee
Ropeburn

68 Via
Centrale
6921 King
Way
86 Chu Street

41-559-87

18-JAN-1991

Molly

Urguhart

3035 Laurier

Hong
Kong
Quebec

418-542-9988

18-JAN-1991

Introduction to Oracle9i: SQL 14-9

Practice 14 (continued)
c. Add the following movie copies in the TITLE_COPY table:
Note: Have the TITLE_ID numbers available for this exercise.

Title
Willie and Christmas Too
Alien Again
The Glob
My Day Off

Miracles on Ice
Soda Gang

Copy_Id
1
1
2
1
1
2
3
1
1

Status
AVAILABLE
AVAILABLE
RENTED
AVAILABLE
AVAILABLE
AVAILABLE
RENTED
AVAILABLE
AVAILABLE

d. Add the following rentals to the RENTAL table:
Note: Title number may be different depending on sequence number.

Title_
Id
92

Copy_
Id
1

Member_
Id
101

Book_date
3 days ago

Exp_Ret_Date
1 day ago

Act_Ret_Date
2 days ago

93
95
97

2
3
1

101
102
106

1 day ago
2 days ago
4 days ago

1 day from now
Today
2 days ago

2 days ago

Introduction to Oracle9i: SQL 14-10

Practice 14 (continued)
5. Create a view named TITLE_AVAIL to show the movie titles and the availability of
each copy and its expected return date if rented. Query all rows from the view. Order the results by
title.
Note: Your results may be different.

6. Make changes to data in the tables.
a. Add a new title. The movie is “Interstellar Wars,” which is rated PG and classified as a
sci-fi movie. The release date is 07-JUL-77. The description is “Futuristic interstellar
action movie. Can the rebels save the humans from the evil empire?” Be sure to add a
title copy record for two copies.
b. Enter two reservations. One reservation is for Carmen Velasquez, who wants to rent
“Interstellar Wars.” The other is for Mark Quick-to-See, who wants to rent “Soda
Gang.”

Introduction to Oracle9i: SQL 14-11

Practice 14 (continued)
c. Customer Carmen Velasquez rents the movie “Interstellar Wars,” copy 1. Remove her
reservation for the movie. Record the information about the rental. Allow the default
value for the expected return date to be used. Verify that the rental was recorded by
using the view you created.
Note: Your results may be different.

7. Make a modification to one of the tables.
a. Add a PRICE column to the TITLE table to record the purchase price of the video.
The column should have a total length of eight digits and two decimal places. Verify
your modifications.

Introduction to Oracle9i: SQL 14-12

Practice 14 (continued)
b. Create a script named lab14_7b.sql that contains update statements that update
each video with a price according to the following list. Run the commands in the
script.
Note: Have the TITLE_ID numbers available for this exercise.

Title
Willie and Christmas Too
Alien Again
The Glob
My Day Off
Miracles on Ice
Soda Gang
Interstellar Wars

Price
25
35
35
35
30
35
29

c. Ensure that in the future all titles contain a price value. Veri fy the constraint.

8. Create a report titled Customer History Report. This report contains each customer’s
history of renting videos. Be sure to include the customer name, movie rented, dates of the rental,
and duration of rentals. Total the number of rentals for all customers for the reporting period. Save
the commands that generate the report in a script file named lab14_8.sql.
Note: Your results may be different.

Introduction to Oracle9i: SQL 14-13

Introduction to Oracle9i: SQL 14-14

Using SET Operators

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives
After completing this lesson, you should be able
to do the following:

•
•

Describe SET operators

•

Control the order of rows returned

Use a SET operator to combine multiple queries into a single
query

15-2

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this lesson, you learn how to write queries by using SET operators.

Introduction to Oracle9i: SQL 15-2

The SET Operators
A

A

B

B

UNION/UNION ALL
A

B

INTERSECT
A

B

MINUS

15-3

Copyright © Oracle Corporation, 2001. All rights reserved.

The SET Operators
The SET operators combine the results of two or more component queries into one result. Queries
containing SET operators are called compound queries.
Operator
UNION
UNION ALL
INTERSECT
MINUS

Returns
All distinct rows selected by either query
All rows selected by either query, including all duplicates
All distinct rows selected by both queries
All distinct rows that are selected by the first SELECT statement and that
are not selected in the second SELECT statement

All SET operators have equal precedence. If a SQL statement contains multiple SET operators, the Oracle
server evaluates them from left (top) to right (bottom) if no parentheses explicitly specify another order.
You should use parentheses to specify the order of evaluation explicitly in queries that use the
INTERSECT operator with other SET operators.
Note: In the slide, the light color (grey) in the diagram represents the query result.

Introduction to Oracle9i: SQL 15-3

Tables Used in This Lesson

The tables used in this lesson are:
• EMPLOYEES: Provides details regarding all
current employees
• JOB_HISTORY: When an employee switches jobs,
the details of the start date and end date of the
former job, the job identification number and
department are recorded in this table

15-4

Copyright © Oracle Corporation, 2001. All rights reserved.

Tables Used in This Lesson
Two tables are used in this lesson. They are the EMPLOYEES table and the JOB_HISTORY table.
The EMPLOYEES table stores the employee details. For the human resource records, this table stores a
unique identification number and email address for each employee. The details of the employee’s job
identification number, salary, and manager are also stored. Some of the employees earn a commission in
addition to their salary; this information is tracked too. The company organizes the roles of employees into
jobs. Some of the employees have been with the company for a long time and have switched to different
jobs. This is monitored using the JOB_HISTORY table. When an employee switches jobs, the details of
the start date and end date of the former job, the job identification number and department are recorded in
the JOB_HISTORY table.
The structure and the data from the EMPLOYEES and the JOB_HISTORY tables are shown on the next
page.
There have been instances in the company of people who have held the same position more than once
during their tenure with the company. For example, consider the employee Taylor, who joined the
company on 24-MAR-1998. Taylor held the job title SA_REP for the period 24-MAR-98 to 31-DEC-98
and the job title SA_MAN for the period 01-JAN-99 to 31-DEC-99. Taylor moved back into the job title of
SA_REP, which is his current job title.
Similarly consider the employee Whalen, who joined the company on 17-SEP-1987. Whalen held the job
title AD_ASST for the period 17-SEP-87 to 17-JUN-93 and the job title AC_ACCOUNT for the period 01JUL-94 to 31-DEC-98. Taylor moved back into the job title of AD_ASST, which is his current job title.

Introduction to Oracle9i: SQL 15-4

Tables Used in This Lesson (continued)
DESC employees

SELECT employee_id, last_name, job_id, hire_date, department_id
FROM employees;

Introduction to Oracle9i: SQL 15-5

Tables Used in This Lesson (continued)
DESC job_history

SELECT * FROM job_history;

Introduction to Oracle9i: SQL 15-6

The UNION SET Operator
A

B

The UNION operator returns results from both queries
after eliminating duplications.

15-7

Copyright © Oracle Corporation, 2001. All rights reserved.

The UNION SET Operator
The UNION operator returns all rows selected by either query. Use the UNION operator to return all rows
from multiple tables and eliminate any duplicate rows.
Guidelines
• The number of columns and the data types of the columns being selected must be identical in all the
SELECT statements used in the query. The names of the columns need not be identical.
• UNION operates over all of the columns being selected.
• NULL values are not ignored during duplicate checking.
• The IN operator has a higher precedence than the UNION operator.
• By default, the output is sorted in ascending order of the first column of the SELECT clause.

Introduction to Oracle9i: SQL 15-7

Using the UNION Operator
Display the current and previous job details of all
employees. Display each employee only once.
SELECT
FROM
UNION
SELECT
FROM

15-8

employee_id, job_id
employees
employee_id, job_id
job_history;

Copyright © Oracle Corporation, 2001. All rights reserved.

Using the UNION SET Operator
The UNION operator eliminates any duplicate records. If there are records that occur both in the
EMPLOYEES and the JOB_HISTORY tables and are identical, the records will be displayed only once.
Observe in the output shown on the slide that the record for the employee with the EMPLOYEE_ID 200
appears twice as the JOB_ID is different in each row.
Consider the following example:
SELECT employee_id, job_id, department_id
FROM
employees
UNION
SELECT employee_id, job_id, department_id
FROM
job_history;

Introduction to Oracle9i: SQL 15-8

Using the UNION SET Operator (continued)
In the preceding output, employee 200 appears three times. Why? Notice the DEPARTMENT_ID values for
employee 200. One row has a DEPARTMENT_ID of 90, another 10, and the third 90. Because of these
unique combinations of job IDs and department IDs, each row for employee 200 is unique and therefore
not considered a duplicate. Observe that the output is sorted in ascending order of the first column of the
SELECT clause, EMPLOYEE_ID in this case.

Introduction to Oracle9i: SQL 15-9

The UNION ALL Operator
A

B

The UNION ALL operator returns results from both
queries including all duplications.

15-10

Copyright © Oracle Corporation, 2001. All rights reserved.

The UNION ALL Operator
Use the UNION ALL operator to return all rows from multiple queries.
Guidelines
• Unlike UNION, duplicate rows are not eliminated and the output is not sorted by default.
• The DISTINCT keyword cannot be used.
Note: With the exception of the above, the guidelines for UNION and UNION ALL are the same.

Introduction to Oracle9i: SQL 15-10

Using the UNION ALL Operator
Display the current and previous departments of
all employees.
SELECT employee_id, job_id, department_id
FROM
employees
UNION ALL
SELECT employee_id, job_id, department_id
FROM
job_history
ORDER BY employee_id;

15-11

Copyright © Oracle Corporation, 2001. All rights reserved.

The UNION ALL Operator (continued)
In the example, 30 rows are selected. The combination of the two tables totals to 30 rows. The UNION
ALL operator does not eliminate duplicate records. The duplicate records are highlighted in the output
shown in the slide. UNION returns all distinct rows selected by either query. UNION ALL returns all rows
selected by either query, including all duplicates. Consider the query on the slide, now written with the
UNION clause:
SELECT
FROM
UNION
SELECT
FROM
ORDER BY

employee_id, job_id,department_id
employees
employee_id, job_id,department_id
job_history
employee_id;

The preceding query returns 29 rows. This is because it eliminates the following row (as it is a duplicate):

Introduction to Oracle9i: SQL 15-11

The INTERSECT Operator
A

B

The INTERSECT operator returns results that are
common to both queries.

15-12

Copyright © Oracle Corporation, 2001. All rights reserved.

The INTERSECT Operator
Use the INTERSECT operator to return all rows common to multiple queries.
Guidelines
• The number of columns and the data types of the columns being selected by the SELECT statements
in the queries must be identical in all the SELECT statements used in the query. The names of the
columns need not be identical.
• Reversing the order of the intersected tables does not alter the result.
• INTERSECT does not ignore NULL values.

Introduction to Oracle9i: SQL 15-12

Using the INTERSECT Operator
Display the employee IDs and job IDs of employees
who are currently in a job title that they have held
once before during their tenure with the company
SELECT employee_id, job_id
FROM
employees
INTERSECT
SELECT employee_id, job_id
FROM
job_history;

15-13

Copyright © Oracle Corporation, 2001. All rights reserved.

The INTERSECT Operator (continued)
In the example in this slide, the query returns only the records that have the same values in the selected
columns in both tables.
What will be the results if you add the DEPARTMENT_ID column to the SELECT statement from the
EMPLOYEES table and add the DEPARTMENT_ID column to the SELECT statement from the
JOB_HISTORY table and run this query? The results may be different because of the introduction of
another column whose values may or may not be duplicates.
Example
SELECT employee_id, job_id, department_id
FROM
employees
INTERSECT
SELECT employee_id, job_id, department_id
FROM
job_history;

Employee 200 is no longer part of the results because the EMPLOYEES.DEPARTMENT_ID value is
different from the JOB_HISTORY.DEPARTMENT_ID value.

Introduction to Oracle9i: SQL 15-13

The MINUS Operator
A

B

The MINUS operator returns rows from the first query
that are not present in the second query.

15-14

Copyright © Oracle Corporation, 2001. All rights reserved.

The MINUS Operator
Use the MINUS operator to return rows returned by the first query that are not present in the second query
(the first SELECT statement MINUS the second SELECT statement).
Guidelines
• The number of columns and the data types of the columns being selected by the SELECT statements
in the queries must be identical in all the SELECT statements used in the query. The names of the
columns need not be identical.
• All of the columns in the WHERE clause must be in the SELECT clause for the MINUS operator to
work.

Introduction to Oracle9i: SQL 15-14

The MINUS Operator
Display the employee IDs of those employees who have
not changed their jobs even once.
SELECT
FROM
MINUS
SELECT
FROM

15-15

employee_id
employees
employee_id
job_history;

Copyright © Oracle Corporation, 2001. All rights reserved.

The MINUS Operator (continued)
In the example in the slide, the employee IDs in the JOB_HISTORY table are subtracted from those in the
EMPLOYEES table. The results set displays the employees remaining after the subtraction; they are
represented by rows that exist in the EMPLOYEES table but do not exist in the JOB_HISTORY table.
These are the records of the employees who have not changed their jobs even once.

Introduction to Oracle9i: SQL 15-15

SET Operator Guidelines
•

The expressions in the SELECT lists must match in
number and data type.

•

Parentheses can be used to alter the sequence of
execution.
The ORDER BY clause:

•

– Can appear only at the very end of the statement
– Will accept the column name, aliases from the first
SELECT statement, or the positional notation

15-16

Copyright © Oracle Corporation, 2001. All rights reserved.

SET Operator Guidelines
• The expressions in the select lists of the queries must match in number and datatype. Queries that use
UNION, UNION ALL, INTERSECT, and MINUS SET operators in their WHERE clause must have
the same number and type of columns in their SELECT list. For example:
SELECT employee_id, department_id
FROM
employees
WHERE (employee_id, department_id)
IN (SELECT employee_id, department_id
FROM
employees
UNION
SELECT employee_id, department_id
FROM
job_history);
• The ORDER BY clause:
– Can appear only at the very end of the statement
– Will accept the column name, an alias, or the positional notation
• The column name or alias, if used in an ORDER BY clause, must be from the first SELECT list.
• SET operators can be used in subqueries.

Introduction to Oracle9i: SQL 15-16

The Oracle Server and SET Operators

15-17

•

Duplicate rows are automatically eliminated except
in UNION ALL.

•

Column names from the first query appear in the
result.

•

The output is sorted in ascending order by default
except in UNION ALL.

Copyright © Oracle Corporation, 2001. All rights reserved.

The Oracle Server and SET Operators
When a query uses SET operators, the Oracle Server eliminates duplicate rows automatically except in the
case of the UNION ALL operator. The column names in the output are decided by the column list in the
first SELECT statement. By default, the output is sorted in ascending order of the first column of the
SELECT clause.
The corresponding expressions in the select lists of the component queries of a compound query must match
in number and datatype. If component queries select character data, the data type of the return values are
determined as follows:
•

If both queries select values of datatype CHAR, the returned values have datatype CHAR.

•

If either or both of the queries select values of datatype VARCHAR2, the returned values
have datatype VARCHAR2.

Introduction to Oracle9i: SQL 15-17

Matching the SELECT Statements
Using the UNION operator, display the department ID,
location, and hire date for all employees.
SELECT
FROM
UNION
SELECT
FROM

15-18

department_id, TO_NUMBER(null) location, hire_date
employees
department_id, location_id,
departments;

TO_DATE(null)

Copyright © Oracle Corporation, 2001. All rights reserved.

Matching the SELECT Statements
As the expressions in the select lists of the queries must match in number , you can use dummy columns
and the data type conversion functions to comply with this rule. In the slide, the name location is given
as the dummy column heading. The TO_NUMBER function is used in the first query to match the NUMBER
data type of the LOCATION_ID column retrieved by the second query. Similarly, the TO_DATE function
in the second query is used to match the DATE datatype of the HIRE_DATE column retrieved by the
second query.

Introduction to Oracle9i: SQL 15-18

Matching the SELECT Statement
Using the UNION operator, display the employee ID,
job ID, and salary of all employees.
SELECT
FROM
UNION
SELECT
FROM

15-19

employee_id, job_id,salary
employees
employee_id, job_id,0
job_history;

Copyright © Oracle Corporation, 2001. All rights reserved.

Matching the SELECT Statement: Example
The EMPLOYEES and JOB_HISTORY tables have several columns in common; for example,
EMPLOYEE_ID, JOB_ID and DEPARTMENT_ID. But what if you want the query to display the
EMPLOYEE_ID, JOB_ID, and SALARY using the UNION operator, knowing that the salary exists only in
the, EMPLOYEES table?
The code example in the slide matches the EMPLOYEE_ID and the JOB_ID columns in the EMPLOYEES
and in the JOB_HISTORY tables. A literal value of 0 is added to the JOB_HISTORY SELECT statement
to match the numeric SALARY column in the EMPLOYEES SELECT statement.
In the preceding results, each row in the output that corresponds to a record from the JOB_HISTORY table
contains a 0 in the SALARY column.

Introduction to Oracle9i: SQL 15-19

Controlling the Order of Rows
Produce an English sentence using two
UNION operators.
COLUMN a_dummy NOPRINT
SELECT 'sing' AS "My dream", 3 a_dummy
FROM dual
UNION
SELECT 'I''d like to teach', 1
FROM dual
UNION
SELECT 'the world to', 2
FROM dual
ORDER BY 2;

15-20

Copyright © Oracle Corporation, 2001. All rights reserved.

Controlling the Order of Rows
By default, the output is sorted in ascending order on the first column. You can use the ORDER BY clause
to change this.
Using ORDER BY to Order Rows
The ORDER BY clause can be used only once in a compound query. If used, the ORDER BY clause must
be placed at the end of the query. The ORDER BY clause accepts the column name, an alias, or the
positional notation. Without the ORDER BY clause, the code example in the slide produces the following
output in the alphabetical order of the first column:

Note: Consider a compound query where the UNION SET operator is used more than once. In this case, the
ORDER BY clause can use only positions rather than explicit expressions.

Introduction to Oracle9i: SQL 15-20

Summary

In this lesson, you should have learned the following:
• UNION returns all distinct rows.

•
•
•
•

15-21

UNION ALL returns all rows, including duplicates.
INTERSECT returns all rows shared by
both queries.
MINUS returns all distinct rows selected by the first
query but not by the second.
ORDER BY can appear only at the very end of
the statement.

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
• The UNION operator returns all rows selected by either query. Use the UNION operator to return all
rows from multiple tables and eliminate any duplicate rows.
• Use the UNION ALL operator to return all rows from multiple queries. Unlike with the UNION
operator, duplicate rows are not eliminated and the output is not sorted by default.
• Use the INTERSECT operator to return all rows common to multiple queries.
• Use the MINUS operator to return rows returned by the first query that are not present in the second
query.
• Remember to use the ORDER BY clause only at the very end of the compound statement.
• Make sure that the corresponding expressions in the SELECT lists match in number and data type.

Introduction to Oracle9i: SQL 15-21

Practice 15 Overview

This practice covers the following topics:
• Writing queries using the SET operators

•

15-22

Discovering alternative join methods

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 15 Overview
In this practice, you write queries using the SET operators.

Introduction to Oracle9i: SQL 15-22

Practice 15
1. List the department IDs for departments that do not contain the job ID ST_CLERK,
using SET operators.

2. Display the country ID and the name of the countries that have no departments located in
them, using SET operators.

3. Produce a list of jobs for departments 10, 50, and 20, in that order. Display job ID and
department ID, using SET operators.

4. List the employee IDs and job IDs of those employees who are currently in the job title that
they have held once before during their tenure with the company.

Introduction to Oracle9i: SQL 15-23

Practice 15 (Continued)
5.

Write a compound query that lists the following:
• Last names and department ID of all the employees from the EMPLOYEES table, irrespective
of the fact whether they belong to any department or not
• Department ID and department name of all the departments from the DEPARTMENTS table,
irrespective of the fact whether they have employees working in them or not.

Introduction to Oracle9i: SQL 15-24

Oracle 9i Datetime Functions

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives
After completing this lesson, you should be able
use the following datetime functions:
• CURRENT_DATE
• CURRENT_TIMESTAMP
• LOCALTIMESTAMP
• DBTIMEZONE
• SESSIONTIMEZONE
• EXTRACT
• FROM_TZ
• TO_TIMESTAMP
• TO_TIMESTAMP_TZ
• TO_YMINTERVAL
• TZ_OFFSET
16-2

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
This lesson addresses some of the datetime functions introduced in Oracle9i.

Introduction to Oracle9i: SQL 16-2

TIME ZONES
GMT

00

00
16-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Time Zones
In Oracle9i, you can include the time zone in your date and time data, as well as provide support for
fractional seconds. This lesson focuses on how to manipulate the new datetime data types included with
Oracle9i using the new datetime functions. To understand the working of these functions, it is necessary to
be familiar with the concept of time zones and Greenwich mean time, or GMT.
The hours of the day are measured by the turning of the earth. The time of day at any particular moment
depends on where you are. When it is noon in Greenwich, England, it is midnight along the international
date line. The earth is divided into 24 time zones, one for each hour of the day. The time along the prime
meridian in Greenwich, England is known as Greenwich mean time, or GMT. GMT is the time standard
against which all other time zones in the world are referenced. It is the same all year round and is not
effected by summer time or daylight savings time. The meridian line is an imaginary line that runs from the
North Pole to the South Pole. It is known as zero longitude and it is the line from which all other lines of
longitude are measured. All time is measured relative to Greenwich mean time (GMT) and all places have
a latitude (their distance north or south of the equator) and a longitude (their distance east or west of the
Greenwich meridian).
Daylight Saving Time
Most western nations advance the clock ahead one hour during the summer months. This period is called
daylight saving time. Daylight saving time lasts from the first Sunday in April to the last Sunday in
October in the most of the United States, Mexico and Canada. The nations of the European Union observe
daylight saving time, but they call it the summer time period. Europe's summer time period begins a week
earlier than its North American counterpart, but ends at the same time.
Introduction to Oracle9i: SQL 16-3

Oracle 9i Datetime Support
•
•

In Oracle9i, you can include the time zone in your
date and time data, and provide support for
fractional seconds.
Three new data types are added to DATE:
– TIMESTAMP
– TIMESTAMP WITH TIME ZONE (TSTZ)
– TIMESTAMP WITH LOCAL TIME ZONE (TSLTZ)

•

16-4

Oracle9i provides daylight savings support for
datetime data types in the server.

Copyright © Oracle Corporation, 2001. All rights reserved.

Oracle 9i Datetime Support
With Oracle9i, three new data types are added to DATE, with the following differences:
Data Type

Time Zone

Fractional Seconds

DATE
TIMESTAMP
TIMESTAMP
(fractional_seconds_
precision) WITH
TIMEZONE

No
No
All values of TIMESTAMP as well
as the time zone displacement value
which indicates the hours and
minutes before or after UTC
(Coordinated Universal Time,
formerly Greenwich mean time).

TIMESTAMP
(fractional_seconds
_precision)
WITH LOCAL TIME ZONE

All values of TIMESTAMP WITH
TIME ZONE, with the following
exceptions:
• Data is normalized to the
database time zone when it
is stored in the database.
• When the data is retrieved,
users see the data in the
session time zone.

No
Yes
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.
Yes

Introduction to Oracle9i: SQL 16-4

Oracle 9i Datetime Support (continued)
TIMESTAMP WITH LOCAL TIME ZONE is stored in the database time zone. When a user selects the
data, the value is adjusted to the user's session time zone.
Example:
A San Francisco database has system time zone = -8:00. When a New York client (session time zone =
-5:00) inserts into or selects from the San Francisco database, TIMESTAMP WITH LOCAL TIME ZONE
data is adjusted as follows:
• The New York client inserts TIMESTAMP '1998-1-23 6:00:00-5:00' into a TIMESTAMP
WITH LOCAL TIME ZONE column in the San Francisco database. The inserted data is stored in
San Francisco as binary value 1998-1-23 3:00:00.
•

When the New York client selects that inserted data from the San Francisco database, the value
displayed in New York is '1998-1-23 6:00:00'.

•

A San Francisco client, selecting the same data, see the value '1998-1-23 3:00:00'.

Support for Daylight Savings Times
The Oracle Server automatically determines, for any given time zone region, whether daylight savings is in
effect and returns local time values based accordingly. The datetime value is sufficient for the server to
determine whether daylight savings time is in effect for a given region in all cases except boundary cases.
A boundary case occurs during the period when daylight savings goes into or comes out of effect. For
example, in the U.S.-Pacific region, when daylight savings comes into effect, the time changes from 2:00
a.m. to 3:00 a.m. The one hour interval between 2 and 3 a.m. does not exist. When daylight savings goes
out of effect, the time changes from 2:00 a.m. back to 1:00 a.m., and the one-hour interval between 1 and 2
a.m. is repeated.
Oracle9i also significantly reduces the cost of developing and deploying applications globally on a single
database instance. Requirements for multigeographic applications include named time zones and
multilanguage support through Unicode. The datetime data types TSLTZ and TSTZ are time-zone-aware.
Datetime values can be specified as local time in a particular region (rather than a particular offset). Using
the time zone rules tables for a given region, the time zone offset for a local time is calculated, taking into
consideration daylight savings time adjustments, and used in further operations.
This lesson addresses some of the new datetime functions introduced in Oracle9i.

Introduction to Oracle9i: SQL 16-5

CURRENT_DATE
ALTER SESSION SET NLS_DATE_FORMAT =
'DD-MON-YYYY HH24:MI:SS';
ALTER SESSION SET TIME_ZONE = '-5:0';
SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL;

ALTER SESSION SET TIME_ZONE = '-8:0';
SELECT SESSIONTIMEZONE, CURRENT_DATE FROM DUAL;

CURRENT_DATE is sensitive to the session time zone

16-6

Copyright © Oracle Corporation, 2001. All rights reserved.

CURRENT_DATE
The CURRENT_DATE function returns the current date in the session’s time zone. The return value is a
date in the Gregorian calendar.
The examples in the slide illustrate that CURRENT_DATE is sensitive to the session time zone. In the first
example, the session is altered to set the TIME_ZONE parameter to –5:0. The TIME_ZONE parameter
specifies the default local time zone displacement for the current SQL session. TIME_ZONE is a session
parameter only, not an initialization parameter. The TIME_ZONE parameter is set as follows:
TIME_ZONE = '[+ | -] hh:mm'
The format mask ([+ | -] hh:mm) indicates the hours and minutes before or after UTC (Coordinated
Universal Time, formerly known as Greenwich mean time).
Observe in the output that the value of CURRENT_DATE changes when the TIME_ZONE parameter
value is changed to –8:0 in the second example.
Note: The ALTER SESSION command sets the date format of the session to
'DD-MON-YYYY HH24:MI:SS' that is Day of month (1-31)-Abbreviated name of month-4-digit year
Hour of day (0-23):Minute (0-59):Second (0-59).

Introduction to Oracle9i: SQL 16-6

CURRENT_TIMESTAMP
ALTER SESSION SET TIME_ZONE = '-5:0';
SELECT SESSIONTIMEZONE, CURRENT_TIMESTAMP FROM DUAL;

ALTER SESSION SET TIME_ZONE = '-8:0';
SELECT SESSIONTIMEZONE, CURRENT_TIMESTAMP FROM DUAL;

16-7

Copyright © Oracle Corporation, 2001. All rights reserved.

CURRENT_TIMESTAMP
The CURRENT_TIMESTAMP function returns the current date and time in the session time zone, as a
value of the data type TIMESTAMP WITH TIME ZONE. The time zone displacement reflects the
current local time of the SQL session. The syntax of the CURRENT_TIMESTAMP function is:
CURRENT_TIMESTAMP (precision)
Where, precision is an optional argument that specifies the fractional second precision of the time
value returned. If you omit precision, the default is 6.
The examples in the slide illustrates that CURRENT_TIMESTAMP is sensitive to the session time zone. In
the first example, the session is altered to set the TIME_ZONE parameter to –5:0. Observe in the output
that the value of CURRENT_TIMESTAMP changes when the TIME_ZONE parameter value is changed to –
8:0 in the second example.

Introduction to Oracle9i: SQL 16-7

LOCALTIMESTAMP
ALTER SESSION SET TIME_ZONE = '-5:0';
SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL;

ALTER SESSION SET TIME_ZONE = '-8:0';
SELECT CURRENT_TIMESTAMP, LOCALTIMESTAMP FROM DUAL;

16-8

Copyright © Oracle Corporation, 2001. All rights reserved.

LOCALTIMESTAMP
The LOCALTIMESTAMP function returns the current date and time in the session time zone in a value of
data type TIMESTAMP. The difference between this function and CURRENT_TIMESTAMP is that
LOCALTIMESTAMP returns a TIMESTAMP value, while CURRENT_TIMESTAMP returns a
TIMESTAMP WITH TIME ZONE value. TIMESTAMP WITH TIME ZONE is a variant of
TIMESTAMP that includes a time zone displacement in its value. The time zone displacement is the
difference (in hours and minutes) between local time and UTC. The TIMESTAMP WITH TIME ZONE
data t ype has the following format:
TIMESTAMP [ (fractional_seconds_precision) ] WITH TIME ZONE
where fractional_seconds_precision optionally specifies the number of digits in the fractional
part of the SECOND datetime field and can be a number in the range 0 to 9. The default is 6. For example,
you specify TIMESTAMP WITH TIME ZONE as a literal as follows:
TIMESTAMP ’1997-01-31 09:26:56.66 +02:00’
The syntax of the LOCAL_TIMESTAMP function is:
LOCAL_TIMESTAMP (TIMESTAMP_precision)
Where, TIMESTAMP_precision is an optional argument that specifies the fractional second precision
of the TIMESTAMP value returned.
The examples in the slide illustrates the difference between LOCALTIMESTAMP and
CURRENT_TIMESTAMP. Observe that the LOCALTIMESTAMP does not display the time zone value,
while the CURRENT_TIMESTAMP does.
Introduction to Oracle9i: SQL 16-8

DBTIMEZONE and SESSIONTIMEZONE

SELECT DBTIMEZONE FROM DUAL;

SELECT SESSIONTIMEZONE FROM DUAL;

16-9

Copyright © Oracle Corporation, 2001. All rights reserved.

DBTIMEZONE and SESSIONTIMEZONE
The default database time zone is the same as the operating system's time zone. You set the database's
default time zone by specifying the SET TIME_ZONE clause of the CREATE DATABASE statement. If
omitted, the default database time zone is the operating system time zone. The database time zone can be
changed for a session with an ALTER SESSION statement.
The DBTIMEZONE function returns the value of the database time zone. The return type is a time zone
offset (a character type in the format ’[+|-]TZH:TZM’) or a time zone region name, depending on how
the user specified the database time zone value in the most recent CREATE DATABASE or ALTER
DATABASE statement. The example on the slide shows that the database time zone is set to UTC, as the
TIME_ZONE parameter is in the format:
TIME_ZONE = '[+ | -] hh:mm'
The SESSIONTIMEZONE function returns the value of the current session’s time zone. The return type is
a time zone offset (a character type in the format ’[+|]TZH:TZM’) or a time zone region name,
depending on how the user specified the session time zone value in the most recent ALTER SESSION
statement. The example in the slide shows that the session time zone is set to UTC.
Observe that the database time zone is different from the current session’s time zone.

Introduction to Oracle9i: SQL 16-9

EXTRACT
SELECT EXTRACT (YEAR FROM SYSDATE) FROM DUAL;

SELECT last_name, hire_date,
EXTRACT (MONTH FROM HIRE_DATE)
FROM employees;
WHERE manager_id = 100;

16-10

Copyright © Oracle Corporation, 2001. All rights reserved.

EXTRACT
The EXTRACT expression extracts and returns the value of a specified datetime field from a datetime or
interval value expression. You can extract any of the components mentioned in the following syntax using
the EXTRACT function. The syntax of the EXTRACT function is:
SELECT EXTRACT ([YEAR] [MONTH][DAY] [HOUR] [MINUTE][SECOND]
[TIMEZONE_HOUR] [TIMEZONE_MINUTE]
[TIMEZONE_REGION] [TIMEZONE_ABBR]
FROM
[datetime_value_expression]
[interval_value_expression]);
When you extract a TIMEZONE_REGION or TIMEZONE_ABBR (abbreviation), the value returned is a
string containing the appropriate time zone name or abbreviation. When you extract any of the other
values, the value returned is in the Gregorian calendar. When extracting from a datetime with a time zone
value, the value returned is in UTC. For a listing of time zone names and their corresponding
abbreviations, query the V$TIMEZONE_NAMES dynamic performance view. In the first example on the
slide, the EXTRACT function is used to extract the YEAR from SYSDATE.
In the second example in the slide, the EXTRACT function is used to extract the MONTH from HIRE_DATE
column of the EMPLOYEES table, for those employees who report to the manager whose EMPLOYEE_ID
is 100.

Introduction to Oracle9i: SQL 16-10

FROM_TZ
SELECT FROM_TZ(TIMESTAMP '2000-03-28 08:00:00','3:00')
FROM DUAL;

16-11

Copyright © Oracle Corporation, 2001. All rights reserved.

FROM_TZ
The FROM_TZ function converts a time stamp value to a TIMESTAMP WITH TIME ZONE value.
The syntax of the FROM_TZ function is as follows:
FROM_TZ(timestamp_value, time_zone_value)
where time_zone_value is a character string in the format 'TZH:TZM' or a character expression that
returns a string in TZR (time zone region) with optional TZD format. 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 savings information. Examples are
'PST' for US/Pacific standard time and 'PDT' for US/Pacific daylight time. To see a listing of valid
values for the TZR and TZD format elements, query the V$TIMEZONE_NAMES dynamic performance
view.
The example in the slide converts a time stamp value to TIMESTAMP WITH TIME ZONE.

Introduction to Oracle9i: SQL 16-11

TO_TIMESTAMP and TO_TIMESTAMP_TZ
SELECT TO_TIMESTAMP ('2000-12-01 11:00:00',
'YYYY-MM-DD HH:MI:SS')
FROM DUAL;

SELECT TO_TIMESTAMP_TZ('1999-12-01 11:00:00 -8:00',
'YYYY-MM-DD HH:MI:SS TZH:TZM')
FROM DUAL;

16-12

Copyright © Oracle Corporation, 2001. All rights reserved.

TO_TIMESTAMP and TO_TIMESTAMP_TZ
The TO_TIMESTAMP function converts a string of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 data type
to a value of TIMESTAMP data type. The syntax of the TO_TIMESTAMP function is:
TO_TIMESTAMP (char,[fmt],['nlsparam'])
The optional fmt specifies the format of char. If you omit fmt, the string must be in the default format
of the TIMESTAMP data type. The optional nlsparam specifies the language in which month and day
names and abbreviations are returned. This argument can have this form:
'NLS_DATE_LANGUAGE = language'
If you omit nlsparams, this function uses the default date language for your session. The example on the
slide converts a character string to a value of TIMESTAMP.
The TO_TIMESTAMP_TZ function converts a string of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 data
type to a value of TIMESTAMP WITH TIME ZONE data type. The syntax of the TO_TIMESTAMP_TZ
function is:
TO_TIMESTAMP_TZ (char,[fmt],['nlsparam'])
The optional fmt specifies the format of char. If omitted, a string must be in the default format of the
TIMESTAMP WITH TIME ZONE data type. The optional nlsparam has the same purpose in this
function as in the TO_TIMESTAMP function. The example in the slide converts a character string to a
value of TIMESTAMP WITH TIME ZONE.
Note: The TO_TIMESTAMP_TZ function does not convert character strings to TIMESTAMP WITH
LOCAL TIME ZONE.
Introduction to Oracle9i: SQL 16-12

TO_YMINTERVAL
SELECT hire_date,
hire_date + TO_YMINTERVAL('01-02') AS
HIRE_DATE_YMININTERVAL
FROM EMPLOYEES
WHERE department_id = 20;

16-13

Copyright © Oracle Corporation, 2001. All rights reserved.

TO_YMINTERVAL
The TO_YMINTERVAL function converts a character string of CHAR, VARCHAR2, NCHAR, or
NVARCHAR2 data type to an INTERVAL YEAR TO MONTH data type. The INTERVAL YEAR TO
MONTH data type stores a period of time using the YEAR and MONTH datetime fields. The format of
INTERVAL YEAR TO MONTH is as follows:
INTERVAL YEAR [(year_precision)] TO MONTH
where year_precision is the number of digits in the YEAR datetime field. The default value of
year_precision is 2.
The syntax of the TO_YMINTERVAL function is:
TO_YMINTERVAL (char)
where char is the character string to be converted.
The example in the slide calculates a date that is one year two months after the hire date for the employees
working in the department 20 of the EMPLOYEES table.
A reverse calculation can also be done using the TO_YMINTERVAL function. For example:
SELECT hire_date, hire_date + TO_YMINTERVAL(' -02-04') AS
HIRE_DATE_YMINTERVAL
FROM EMPLOYEES WHERE department_id = 20;
Observe that the character string passed to the TO_YMINTERVAL function has a negative value. The
example returns a date that is two years and four months before the hire date for the employees working in
the department 20 of the EMPLOYEES table.
Introduction to Oracle9i: SQL 16-13

TZ_OFFSET
SELECT TZ_OFFSET('US/Eastern') FROM DUAL;

SELECT TZ_OFFSET('Canada/Yukon') FROM DUAL;

SELECT TZ_OFFSET('Europe/London') FROM DUAL;

16-14

Copyright © Oracle Corporation, 2001. All rights reserved.

TZ_OFFSET
The TZ_OFFSET function returns the time zone offset corresponding to the value entered. The return
value is dependent on the date when the statement is executed. For example if the TZ_OFFSET function
returns a value -08:00, the return value can be interpreted as the time zone from where the command was
executed is eight hours after UTC. You can enter a valid time zone name, a time zone offset from UTC
(which simply returns itself), or the keyword SESSIONTIMEZONE or DBTIMEZONE. The syntax of the
TZ_OFFSET function is:
TZ_OFFSET ( ['time_zone_name'] '[+ | -] hh:mm' ]
[ SESSIONTIMEZONE] [DBTIMEZONE])
The examples in the slide can be interpreted as follows:
• The time zone ‘US/Eastern’ is five hours behind UTC
•

The time zone ‘Canada/Yukon’ is eight hours behind UTC

•

The time zone ‘Europe/London’ is in the UTC

For a listing of valid time zone name values, query the V$TIMEZONE_NAMES dynamic performance
view.
DESC V$TIMEZONE_NAMES

Introduction to Oracle9i: SQL 16-14

TZ_OFFSET (continued)
SELECT * FROM

V$TIMEZONE_NAMES;

Introduction to Oracle9i: SQL 16-15

Summary
In this lesson, you should have learned how to use
the following functions:
• CURRENT_DATE
• FROM_TZ
• CURRENT_TIMESTAMP
• TO_TIMESTAMP
• LOCALTIMESTAMP
• TO_TIMESTAMP_TZ
• DBTIMEZONE
• TO_YMINTERVAL
• SESSIONTIMEZONE
• TZ_OFFSET
• EXTRACT

16-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
This lesson addressed some of the new datetime functions introduced in Oracle9i.

Introduction to Oracle9i: SQL 16-16

Practice 16 Overview
This practice covers using the Oracle9i datetime
functions.

16-17

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 16 Overview
In this practice, you display time zone offsets, CURRENT_DATE, CURRENT_TIMESTAMP, and the
LOCALTIMESTAMP. You also set time zones and use the EXTRACT function.

Introduction to Oracle9i: SQL 16-17

Practice 16
1. Alter the session to set the NLS_DATE_FORMAT to DD-MON-YYYY HH24:MI:SS.
2.

a. Write queries to display the time zone offsets (TZ_OFFSET), for the following time
zones.
–

US/Pacific-New

–

Singapore

–

Egypt

b. Alter the session to set the TIME_ZONE parameter value to the time zone offset of
US/Pacific-New.
c. Display the CURRENT_DATE, CURRENT_TIMESTAMP, and LOCALTIMESTAMP for
this session.
Note: The output might be different based on the date when the command is
executed.

d. Alter the session to set the TIME_ZONE parameter value to the time zone offset of
Singapore.
e. Display the CURRENT_DATE, CURRENT_TIMESTAMP, and LOCALTIMESTAMP for
this session. Note: The output might be different based on the date when the command is
executed.

Note: Observe in the preceding practice that CURRENT_DATE, CURRENT_TIMESTAMP, and
LOCALTIMESTAMP are all sensitive to the session time zone.
3.

Write a query to display the DBTIMEZONE and SESSIONTIMEZONE.

Introduction to Oracle9i: SQL 16-18

Practice 16 (continued)
4.

Write a query to extract the YEAR from HIRE_DATE column of the EMPLOYEES table for those
employees who work in department 80.

Introduction to Oracle9i: SQL 16-19

Introduction to Oracle9i: SQL 16-20

Enhancements to the
GROUP BY Clause

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this lesson, you should be able
to do the following:

•
•
•
•

Use the ROLLUP operation to produce
subtotal values
Use the CUBE operation to produce crosstabulation values
Use the GROUPING function to identify the row
values created by ROLLUP or CUBE
Use GROUPING SETS to produce a single result set

Copyright © Oracle Corporation, 2001. All rights reserved.

17-2

Lesson Aim
In this lesson you learn how to:
•

Group data for obtaining the following:
– Subtotal values by using the ROLLUP operator
– Cross-tabulation values by using the CUBE operator

•

Use the GROUPING function to identify the level of aggregation in the results set produced by a
ROLLUP or CUBE operator.

•

Use GROUPING SETS to produce a single result set that is equivalent to a UNION ALL approach

Introduction to Oracle9i: SQL 17-2

Review of Group Functions
Group functions operate on sets of rows to give one
result per group.
SELECT
FROM
[WHERE
[GROUP BY
[ORDER BY

[column,] group_function(column). . .
table
condition]
group_by_expression]
column];

Example:
SELECT AVG(salary), STDDEV(salary),
COUNT(commission_pct),MAX(hire_date)
FROM employees
WHERE job_id LIKE 'SA%';

17-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Group Functions
You can use the GROUP BY clause to divide the rows in a table into groups. You can then use the group
functions to return summary information for each group. Group functions can appear in select lists and in
ORDER BY and HAVING clauses. The Oracle Server applies the group functions to each group of rows
and returns a single result row for each group.
Types of Group Functions
Each of the group functions AVG, SUM, MAX, MIN, COUNT, STDDEV, and VARIANCE accept one
argument. The functions AVG, SUM, STDDEV, and VARIANCE operate only on numeric values. MAX and
MIN can operate on numeric, character, or date data values. COUNT returns the number of nonnull rows for
the given expression. The example in the slide calculates the average salary, standard deviation on the
salary, number of employees earning a commission and the maximum hire date for those employees whose
JOB_ID begins with SA.
Guidelines for Using Group Functions
• The data types for the arguments can be CHAR, VARCHAR2, NUMBER, or DATE.
• All group functions except COUNT(*) ignore null values. To substitute a value for null values, use
the NVL function. COUNT returns either a number or zero.
•

The Oracle Server implicitly sorts the result set in ascending order of the grouping columns
specified, when you use a GROUP BY clause. To override this default ordering, you can use DESC
in an ORDER BY clause.

Introduction to Oracle9i: SQL 17-3

Review of the GROUP BY Clause
Syntax:
SELECT
FROM
[WHERE
[GROUP BY
[ORDER BY

[column,] group_function(column). . .
table
condition]
group_by_expression]
column];

Example:
SELECT department_id, job_id, SUM(salary),
COUNT(employee_id)
FROM
employees
GROUP BY department_id, job_id;

17-4

Copyright © Oracle Corporation, 2001. All rights reserved.

Review of GROUP BY Clause
The example illustrated in the slide is evaluated by the Oracle Server as follows:
• The SELECT clause specifies that the following columns are to be retrieved:
– Department ID and job ID columns from the EMPLOYEES table
– The sum of all the salaries and the number of employees in each group that you have
specified in the GROUP BY clause
• The GROUP BY clause specifies how the rows should be grouped in the table. The total salary and
the number of employees are calculated for each job ID within each department. The rows are
grouped by department ID and then grouped by job within each department.

Introduction to Oracle9i: SQL 17-4

Review of the HAVING Clause
SELECT
FROM
[WHERE
[GROUP BY
[HAVING
[ORDER BY

17-5

[column,] group_function(column). . .
table
condition]
group_by_expression]
having_expression];
column];

•

Use the HAVING clause to specify which groups
are to be displayed.

•

You further restrict the groups on the basis of a
limiting condition.

Copyright © Oracle Corporation, 2001. All rights reserved.

The HAVING Clause
Groups are formed and group functions are calculated before the HAVING clause is applied to the groups.
The HAVING clause can precede the GROUP BY clause, but it is recommended that you place the GROUP
BY clause first because it is more logical.
The Oracle Server performs the following steps when you use the HAVING clause:
1. Groups rows
2. Applies the group functions to the groups and displays the groups that match the criteria in the
HAVING clause
SELECT department_id, AVG(salary)
FROM employees
GROUP BY department_id
HAVING AVG(salary) >9500;

The example displays department ID and average salary for those departments whose average salary is
greater than $9,500.

Introduction to Oracle9i: SQL 17-5

GROUP BY with ROLLUP and
CUBE Operators
•
•
•

17-6

Use ROLLUP or CUBE with GROUP BY to produce
superaggregate rows by cross-referencing
columns.
ROLLUP grouping produces a results set
containing the regular grouped rows and the
subtotal values.
CUBE grouping produces a results set containing
the rows from ROLLUP and cross-tabulation rows.

Copyright © Oracle Corporation, 2001. All rights reserved.

GROUP BY with the ROLLUP and CUBE Operators
You specify ROLLUP and CUBE operators in the GROUP BY clause of a query. ROLLUP grouping
produces a results set containing the regular grouped rows and subtotal rows. The CUBE operation in the
GROUP BY clause groups the selected rows based on the values of all possible combinations of
expressions in the specification and returns a single row of sum mary information for each group. You can
use the CUBE operator to produce cross-tabulation rows.
Note: When working with ROLLUP and CUBE, make sure that the columns following the GROUP BY
clause have meaningful, real-life relationships with each other; otherwise the operators retu rn irrelevant
information.
The ROLLUP and CUBE operators are available only in Oracle8i and later releases.

Introduction to Oracle9i: SQL 17-6

ROLLUP Operator

SELECT
FROM
[WHERE
[GROUP BY
[HAVING
[ORDER BY

•
•

[column,] group_function(column). . .
table
condition]
[ROLLUP] group_by_expression ]
having_expression];
column];

ROLLUP is an extension to the GROUP BY clause.
Use the ROLLUP operation to produce cumulative
aggregates such as subtotals.

17-7

Copyright © Oracle Corporation, 2001. All rights reserved.

The ROLLUP Operator
The ROLLUP operator delivers aggregates and superaggregates for expressions within a GROUP BY
statement. The ROLLUP operator can be used by report writers to extract statistics and summary
information from results sets. The cumulative aggregates can be used in reports, charts, and graphs.
The ROLLUP operator creates groupings by moving in one direction, from right to left, along the list of
columns specified in the GROUP BY clause. It then applies the aggregate function to these groupings.
Note: To produce subtotals in n dimensions (that is, n columns in the GROUP BY clause) without a
ROLLUP operator, n+1 SELECT statements must be linked with UNION ALL. This makes the query
execution inefficient, because each of the SELECT statements causes table access. The ROLLUP operator
gathers its results with just one table access. The ROLLUP operator is useful if there are many columns
involved in producing the subtotals.

Introduction to Oracle9i: SQL 17-7

ROLLUP Operator Example
SELECT
department_id, job_id, SUM(salary)
FROM
employees
WHERE department_id < 60
GROUP BY ROLLUP(department_id, job_id);

1
2

3

17-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Example of a ROLLUP Operator
In the example in the slide:
•
•

Total salaries for every job ID within a department for those departments whose department ID is
less than 60 are displayed by the GROUP BY clause (labeled 1)
The ROLLUP operator displays:

– Total salary for those departments whose department ID is less than 60 (labeled 2)
– Total salary for all departments whose department ID is less than 60, irrespective of the job
IDs (labeled 3)
• All rows indicated as 1 are regular rows and all rows indicated as 2 and 3 are superaggregate rows.
The ROLLUP operator creates subtotals that roll up from the most detailed level to a grand total, following
the grouping list specified in the GROUP BY clause. First it calculates the standard aggregate values for the
groups specified in the GROUP BY clause (in the example, the sum of salaries grouped on each job within
a department). Then it creates progressively higher-level subtotals, moving from right to left through the
list of grouping columns. (In the preceding example, the sum of salaries for each department is calculated,
followed by the sum of salaries for all departments.)
• Given n expressions in the ROLLUP operator of the GROUP BY clause, the operation results in n + 1
= 2 + 1 = 3 groupings.
•

Rows based on the values of the first n expressions are called rows or regular rows and the others are
called superaggregate rows.

Introduction to Oracle9i: SQL 17-8

CUBE Operator

SELECT
FROM
[WHERE
[GROUP BY
[HAVING
[ORDER BY

•
•

[column,] group_function(column). . .
table
condition]
[CUBE] group_by_expression]
having_expression];
column];

CUBE is an extension to the GROUP BY clause.
You can use the CUBE operator to produce crosstabulation values with a single SELECT statement.

17-9

Copyright © Oracle Corporation, 2001. All rights reserved.

The CUBE Operator
The CUBE operator is an additional switch in the GROUP BY clause in a SELECT statement. The CUBE
operator can be applied to all aggregate functions, including AVG, SUM, MAX, MIN, and COUNT. It is used
to produce results sets that are typically used for cross-tabular reports. While ROLLUP produces only a
fraction of possible subtotal combinations, CUBE produces subtotals for all possible combinations of
groupings specified in the GROUP BY clause, and a grand total.
The CUBE operator is used with an aggregate function to generate additional rows in a results set. Columns
included in the GROUP BY clause are cross-referenced to produce a superset of groups. The aggregate
function specified in the select list is applied to these groups to produce summary values for the additional
superaggregate rows. The number of extra groups in the results set is determined by the number of columns
included in the GROUP BY clause.
In fact, every possible combination of the columns or expressions in the GROUP BY clause is used to
produce superaggregates. If you have n columns or expressions in the GROUP BY clause, there will be 2 n
possible superaggregate combinations. Mathematically, these combinations form an
n-dimensional cube, which is how the operator got its name.
By using application or programming tools, these superaggregate values can then be fed into charts and
graphs that convey results and relationships visually and effectively.

Introduction to Oracle9i: SQL 17-9

CUBE Operator: Example
SELECT department_id, job_id, SUM(salary)
FROM
employees
WHERE
department_id < 60
GROUP BY CUBE (department_id, job_id);

1
2

3
4

17-10

Copyright © Oracle Corporation, 2001. All rights reserved.

Example of a CUBE Operator
The output of the SELECT statement in the example can be interpreted as follows:
• The total salary for every job within a department (for those departments whose department ID is less
than 50) is displayed by the GROUP BY clause (labeled 1)
• The total salary for those departments whose department ID is less than 50 (labeled 2)
• The total salary for every job irrespective of the department (labeled 3)
• Total salary for those departments whose department ID is less than 50, irrespective of the job titles
(labeled 4)
In the preceding example, all rows indicated as 1 are regular rows, all rows indicated as 2 and 4 are
superaggregate rows, and all rows indicated as 3 are cross-tabulation values.
The CUBE operator has also performed the ROLLUP operation to display the subtotals for those departments
whose department ID is less than 50 and the total salary for those departments whose department ID is less
than 50, irrespective of the job titles. Additionally, the CUBE operator displays the total salary for every job
irrespective of the department.
Note: Similar to the ROLLUP operator, producing subtotals in n dimensions (that is, n columns in the GROUP
BY clause) without a CUBE operator requires 2n SELECT statements to be linked with UNION ALL. Thus, a
report with three dimensions requires 2 3 = 8 SELECT statements to be linked with UNION ALL.

Introduction to Oracle9i: SQL 17-10

GROUPING Function
SELECT
[column,] group_function(column) . ., GROUPING(expr)
FROM
table
[WHERE
condition]
[GROUP
BY [ROLLUP][CUBE] group_by_expression ]
[HAVING having_expression];
[ORDER BY
column];

•

The GROUPING function can be used with either the
CUBE or ROLLUP operator.

•

Using it, you can find the groups forming the
subtotal in a row.
Using it, you can differentiate stored NULL values
from NULL values created by ROLLUP or CUBE.

•
•
17-11

It returns 0 or 1.
Copyright © Oracle Corporation, 2001. All rights reserved.

The GROUPING Function
The GROUPING function can be used with either the CUBE or ROLLUP operator to help you understand how
a summary value has been obtained.
The GROUPING function uses a single column as its argument. The expr in the GROUPING function must
match one of the expressions in the GROUP BY clause. The function returns a value of 0 or 1.
The values returned by the GROUPING function are useful to:
• Determine the level of aggregation of a given subtotal; that is, the group or groups on which the
subtotal is based
• Identify whether a NULL value in the expression column of a row of the result set indicates:
– A NULL value from the base table (stored NULL value)
– A NULL value created by ROLLUP/CUBE (as a result of a group function on that expression)
A value of 0 returned by the GROUPING function based on an expression indicates one of the following:
• The expression has been used to calculate the aggregate value.
• The NULL value in the expression column is a stored NULL value.
A value of 1 returned by the GROUPING function based on an expression indicates one of the following:
• The expression has not been used to calculate the aggregate value.
• The NULL value in the expression column is created by ROLLUP or CUBE as a result of grouping.

Introduction to Oracle9i: SQL 17-11

GROUPING Function: Example
SELECT
department_id DEPTID, job_id JOB, SUM(salary),
GROUPING(department_id) GRP_DEPT,GROUPING(job_id) GRP_JOB
FROM
employees
WHERE department_id < 50
GROUP BY ROLLUP(department_id, job_id);

17-12

Copyright © Oracle Corporation, 2001. All rights reserved.

Example of a GROUPING Function
In the example in the slide, consider the summary value 4400 in the first row. This summary value is the
total salary for the job ID of AD_ASST within department 10. To calculate this summary value, both the
columns DEPARTMENT_ID and JOB_ID have been taken into account. Thus a value of 0 is returned for
both the expressions GROUPING(department_id) and GROUPING(job_id).
Consider the summary value 4400 in the second row. This value is the total salary for department 10 and
has been calculated by taking into account the column DEPARTMENT_ID; thus a value of 0 has been
returned by GROUPING(department_id). Because the column JOB_ID has not been taken into
account to calculate this value, a value of 1 has been returned for GROUPING(job_id). You can
observe similar output in the fifth row.
In the last row, consider the summary value 23400. This is the total salary for those departments whose
department ID is less than 50 and all job titles. To calculate this summary value, neither of the columns
DEPARTMENT_ID and JOB_ID have been taken into account. Thus a value of 1 is returned for both the
expressions GROUPING(department_id) and GROUPING(job_id).

Introduction to Oracle9i: SQL 17-12

GROUPING SETS

•

GROUPING SETS are a further extension of the
GROUP BY clause.

•
•

You can use GROUPING SETS to define multiple
groupings in the same query.
The Oracle Server computes all groupings specified
in the GROUPING SETS clause and combines the
results of individual groupings with a UNION ALL
operation.

•

Grouping set efficiency:
– Only one pass over the base table is required.
– There is no need to write complex UNION statements.
– The more elements the GROUPING SETS have, the
higher the performance benefit is.

17-13

Copyright © Oracle Corporation, 2001. All rights reserved.

GROUPING SETS
GROUPING SETS are a further extension of the GROUP BY clause that let you specify multiple
groupings of data. Doing so facilitates efficient aggregation and hence facilitates analysis of data across
multiple dimensions.
A single SELECT statement can now be written using GROUPING SETS to specify various groupings
(that can also include ROLLUP or CUBE operators), rather than multiple SELECT statements combined by
UNION ALL operators. For example, you can say:
SELECT department_id, job_id, manager_id, AVG(salary)
FROM employees
GROUP BY
GROUPING SETS
((department_id, job_id, manager_id),
(department_id, manager_id),(job_id, manager_id));
This statement calculates aggregates over three groupings:
(department_id, job_id, manager_id), (department_id, manager_ id)
and (job_id, manager_id)
Without this enhancement in Oracle9i, multiple queries combined together with UNION ALL are required
to get the output of the preceding SELECT statement. A multiquery approach is inefficient, for it requires
multiple scans of the same data.

Introduction to Oracle9i: SQL 17-13

GROUPING SETS (continued)
Compare the preceding statement with this alternative:
SELECT department_id, job_id, manager_id, AVG(salary)
FROM employees
GROUP BY CUBE(department_id, job_id, manager_id);
The preceding statement computes all the 8 (2 *2 *2) groupings, though only the groups
(department_id, job_id, manager_id), (department_id, manager_id) and
(job_id, manager_id)are of interest to you.
Another alternative is the following statement:
SELECT department_id, job_id, manager_id, AVG(salary)
FROM employees
GROUP BY department_id, job_id, manager_id
UNION ALL
SELECT department_id, NULL, manager_id, AVG(salary)
FROM employees
GROUP BY department_id, manager_id
UNION ALL
SELECT NULL, job_id, manager_id, AVG(salary)
FROM employees
GROUP BY job_id, manager_id;
This statement requires three scans of the base table, making it inefficient.
CUBE and ROLLUP can be thought of as grouping sets with very specific semantics. The following
equivalencies show this fact:
CUBE(a, b, c)
is equivalent to

GROUPING SETS
((a, b, c), (a, b), (a, c), (b, c),
(a), (b), (c), ())

ROLLUP(a, b,c)

GROUPING SETS ((a, b, c), (a, b),(a), ())

is equivalent to

Introduction to Oracle9i: SQL 17-14

GROUPING SETS: Example
SELECT department_id, job_id, manager_id, avg(salary)
FROM
employees
GROUP BY GROUPING SETS
((department_id,job_id), (job_id,manager_id));

1

2

17-15

Copyright © Oracle Corporation, 2001. All rights reserved.

GROUPING SETS: Example
The query in the slide calculates aggregates over two groupings. The table is divided into the following
groups:
•
•

Department ID, Job ID
Job ID, Manager ID

The average salaries for each of these groups are calculated. The results set displays average salary for
each of the two groups.
In the output, the group marked as 1 can be interpreted as:
• The average salary of all employees with the job ID AD_ASST in the department 10 is 4400.
•

The average salary of all employees with the job ID MK_MAN in the department 20 is 13000.

•

The average salary of all employees with the job ID MK_REP in the department 20 is 6000.

•

The average salary of all employees with the job ID ST_CLERK in the department 50 is 2925 and so
on.

Introduction to Oracle9i: SQL 17-15

GROUPING SETS: Example (continued)
The group marked as 2 in the output is interpreted as:
• The average salary of all employees with the job ID MK_MAN, who report to the manager with the
manager ID 100, is 13000.
• The average salary of all employees with the job ID MK_REP, who report to the manager with the
manager ID 201, is 6000, and so on.
The example in the slide can also be written as:
SELECT department_id, job_id, NULL as manager_id,
AVG(salary) as AVGSAL
FROM employees
GROUP BY department_id, job_id
UNION ALL
SELECT NULL, job_id, manager_id, avg(salary) as AVGSAL
FROM employees
GROUP BY job_id, manager_id;
In the absence of an optimizer that looks across query blocks to generate the execution plan, the preceding
query would need two scans of the base table, EMPLOYEES. This could be very inefficient. Hence the
usage of the GROUPING SETS statement is recommended.

Introduction to Oracle9i: SQL 17-16

Composite Columns
•

A composite column is a collection of columns
that are treated as a unit.
ROLLUP (a,(b,c) , d)

•

To specify composite columns, in the GROUP BY
clause you group columns within parentheses so
that the Oracle server treats them as a unit while
computing ROLLUP or CUBE operations.

•

When used with ROLLUP or CUBE, composite
columns would mean skipping aggregation across
certain levels.

17-17

Copyright © Oracle Corporation, 2001. All rights reserved.

Composite Columns
A composite column is a collection of columns that are treated as a unit during the computation of
groupings. You specify the columns in parentheses as in the following statement:
ROLLUP (a, (b, c), d)
Here, (b,c) form a composite column and are treated as a unit. In general, composite columns are useful
in ROLLUP, CUBE, and GROUPING SETS. For example, in CUBE or ROLLUP, composite columns
would mean skipping aggregation across certain levels.
That is, GROUP BY ROLLUP(a, (b, c))
is equivalent to
GROUP BY a, b, c UNION ALL
GROUP BY a UNION ALL
GROUP BY ()
Here, (b, c) are treated as a unit and rollup will not be applied across (b, c). It is as if you have an
alias, for example z, for (b, c), and the GROUP BY expression reduces to
GROUP BY ROLLUP(a, z).
Note: GROUP BY( ) is typically a SELECT statement with NULL values for the columns a and b and
only the aggregate function. This is generally used for generating the grand totals.
SELECT NULL, NULL, aggregate_col
FROM 
GROUP BY ( );
Introduction to Oracle9i: SQL 17-17

Composite Columns (continued)
Compare this with the normal ROLLUP as in:
GROUP BY ROLLUP(a, b, c)
which would be
GROUP BY
GROUP BY
GROUP BY
GROUP BY

a, b, c UNION ALL
a, b UNION ALL
a UNION ALL
().

Similarly,
GROUP BY CUBE((a, b), c)
would be equivalent to
GROUP BY a, b, c UNION ALL
GROUP BY a, b UNION ALL
GROUP BY c UNION ALL
GROUP By ()
The following table shows grouping sets specification and equivalent GROUP BY specification.
GROUPING SETS Statements

Equivalent GROUP BY Statements

GROUP BY GROUPING SETS(a, b, c)

GROUP BY a UNION ALL
GROUP BY b UNION ALL
GROUP BY c

GROUP BY GROUPING SETS(a, b,(b, c))
(The GROUPING SETS expression has a composite
column)

GROUP BY a UNION ALL
GROUP BY b UNION ALL
GROUP BY b, c

GROUP BY GROUPING SETS((a, b, c))

GROUP BY a, b, c

GROUP BY GROUPING SETS(a, (b), ())

GROUP BY a UNION ALL
GROUP BY b UNION ALL
GROUP BY ()

GROUP BY GROUPING SETS
(a,ROLLUP(b, c))
(The GROUPING SETS expression has a composite
column)

GROUP BY a UNION ALL
GROUP BY ROLLUP(b, c)

Introduction to Oracle9i: SQL 17-18

Composite Columns: Example
SELECT
department_id, job_id, manager_id, SUM(salary)
FROM
employees
GROUP BY ROLLUP( department_id,(job_id, manager_id));

2

1

3

17-19

Copyright © Oracle Corporation, 2001. All rights reserved.

Composite Columns: Example
Consider the example:
SELECT department_id, job_id,manager_id, SUM(salary)
FROM
employees
GROUP BY ROLLUP( department_id,job_id, manager_id);
The preceding query results in the Oracle Server computing the following groupings:
1. (department_id, job_id, manager_id)
2. (department_id, job_id)
3. (department_id)
4. ( )
If you are just interested in grouping of lines (1), (3), and (4) in the preceding example, you cannot limit the
calculation to those groupings without using composite columns. With composite columns, this is possible by
treating JOB_ID and MANAGER_ID columns as a single unit while rolling up. Columns enclosed in
parentheses are treated as a unit while computing ROLLUP and CUBE. This is illustrated in the example on the
slide. By enclosing JOB_ID and MANAGER_ID columns in parenthesis, we indicate to the Oracle Server to
treat JOB_ID and MANAGER_ID as a single unit, as a composite column.

Introduction to Oracle9i: SQL 17-19

Composite Columns Example (continued)
The example in the slide computes the following groupings:
• (department_id, job_id, manager_id)
•

(department_id)

•

( )

The example in the slide displays the following:
• Total salary for every department (labeled 1)
• Total salary for every department, job ID, and manager (labeled 2)
• Grand total (labeled 3)
The example in the slide can also be written as:
SELECT department_id, job_id, manager_id, SUM(salary)
FROM
employees
GROUP BY department_id,job_id, manager_id
UNION ALL
SELECT department_id, TO_CHAR(NULL),TO_NUMBER(NULL), SUM(salary)
FROM
employees
GROUP BY department_id
UNION ALL
SELECT TO_NUMBER(NULL), TO_CHAR(NULL),TO_NUMBER(NULL), SUM(sala ry)
FROM
employees
GROUP BY ();
In the absence of an optimizer that looks across query blocks to generate the execution plan, the preceding query
would need three scans of the base table, EMPLOYEES. This could be very inefficient. Hence, the use of composite
columns is recommended.

Introduction to Oracle9i: SQL 17-20

Concatenated Groupings
•

Concatenated groupings offer a concise way to
generate useful combinations of groupings.

•

To specify concatenated grouping sets, you
separate multiple grouping sets, ROLLUP, and
CUBE operations with commas so that the Oracle
Server combines them into a single GROUP BY
clause.

•

The result is a cross-product of groupings from
each grouping set.
GROUP BY GROUPING SETS(a, b), GROUPING SETS(c, d)

17-21

Copyright © Oracle Corporation, 2001. All rights reserved.

Concatenated Columns
Concatenated groupings offer a concise way to generate useful combinations of groupings. The
concatenated groupings are specified simply by listing multiple grouping sets, cubes, and rollups, and
separating them with commas. Here is an example of concatenated grouping sets:
GROUP BY GROUPING SETS(a, b), GROUPING SETS(c, d)
The preceding SQL defines the following groupings:
(a, c), (a, d), (b, c), (b, d)
Concatenation of grouping sets is very helpful for these reasons:
• Ease of query development: you need not enumerate all groupings manually
• Use by applications: SQL generated by OLAP applications often involves concatenation of
grouping sets, with each grouping set defining groupings needed for a dimension

Introduction to Oracle9i: SQL 17-21

Concatenated Groupings Example
SELECT
department_id, job_id, manager_id, SUM(salary)
FROM
employees
GROUP BY department_id,ROLLUP(job_id),CUBE(manager_id);
1

2
3
4

17-22

Copyright © Oracle Corporation, 2001. All rights reserved.

Concatenated Groupings Example
The example in the slide results in the following groupings:
• (department_id, manager_id, job_id )
•

(department_id, manager_id)

•

(department_id, job_id)

•

(department_id)

The total salary for each of these groups is calculated.
The example in the slide displays the following:
•

Total salary for every department, job ID, manager (labeled 1)

•

Total salary for every department, manager ID (labeled 2)

•

Total salary for every department, job ID (labeled 3)

•

Total salary for every department (labeled 4)

For easier understanding, the details for the department 10 are highlighted in the output.

Introduction to Oracle9i: SQL 17-22

Summary
In this lesson, you should have learned how to:
• Use the ROLLUP operation to produce
subtotal values
• Use the CUBE operation to produce cross-tabulation
values
• Use the GROUPING function to identify the row values
created by ROLLUP or CUBE
• Use the GROUPING SETS syntax to define multiple
groupings in the same query.
• Use the GROUP BY clause, to combine expressions in
various ways:
– Composite columns
– Concatenated grouping sets

17-23

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
• ROLLUP and CUBE are extensions of the GROUP BY clause.
•

ROLLUP is used to display subtotal and grand total values.

•

CUBE is used to display cross-tabulation values.

•

The GROUPING function helps you determine whether a row is an aggregate produced by a CUBE or
ROLLUP operator.

•

With the GROUPING SETS syntax, you can define multiple groupings in the same query. GROUP
BY computes all the groupings specified and combines them with UNION ALL.

•

Within the GROUP BY clause, you can combine expressions in various ways:
– To specify composite columns, you group columns within parentheses so that the Oracle
Server treats them as a unit while computing ROLLUP or CUBE operations.
– To specify concatenated grouping sets, you separate multiple grouping sets, ROLLUP, and
CUBE operations with commas so that the Oracle Server combines them into a single GROUP
BY clause. The result is a cross-product of groupings from each grouping set.

Introduction to Oracle9i: SQL 17-23

Practice 17 Overview

This practice covers the following topics:
• Using the ROLLUP operator

•
•
•

17-24

Using the CUBE operator
Using the GROUPING function
Using GROUPING SETS

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 17 Overview
In this practice, you use the ROLLUP and CUBE operators as extensions of the GROUP BY clause. You
will also use GROUPING SETS.

Introduction to Oracle9i: SQL 17-24

Practice 17
1. Write a query to display the following for those employees whose manager ID is less than 120:
– Manager ID
– Job ID and total salary for every job ID for employees who report to the same manager
– Total salary of those managers
– Total salary of those managers, irrespective of the job IDs

Introduction to Oracle9i: SQL 17-25

Practice 17 (continued)
2. Observe the output from question 1. Write a query using the GROUPING function to determine
whether the NULL values in the columns corresponding to the GROUP BY expressions are
caused by the ROLLUP operation.

Introduction to Oracle9i: SQL 17-26

Practice 17 (continued)
3. Write a query to display the following for those employees whose manager ID is less than 120 :
– Manager ID
– Job and total salaries for every job for employees who report to the same manager
– Total salary of those managers
– Cross-tabulation values to display the total salary for every job, irrespective of the
manager
– Total salary irrespective of all job titles

Introduction to Oracle9i: SQL 17-27

Practice 17 (continued)
4. Observe the output from question 3. Write a query using the GROUPING function to
determine whether the NULL values in the columns corresponding to the GROUP BY
expressions are caused by the CUBE operation.

Introduction to Oracle9i: SQL 17-28

Practice 17 (continued)
5. Using GROUPING SETS, write a query to display the following groupings :
–

department_id, manager_id, job_id

–

department_id, job_id

–

manager_id, job_id

The query should calculate the sum of the salaries for each of these groups.

Introduction to Oracle9i: SQL 17-29

Introduction to Oracle9i: SQL 17-30

Introduction to Oracle9i: SQL 17-31

Introduction to Oracle9i: SQL 17-32

Advanced Subqueries

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives
After completing this lesson, you should be able
to do the following:

•
•
•
•
•
•
•
•
•
18-2

Write a multiple-column subquery
Describe and explain the behavior of subqueries when
null values are retrieved
Write a subquery in a FROM clause
Use scalar subqueries in SQL
Describe the types of problems that can be solved with
correlated subqueries
Write correlated subqueries
Update and delete rows using correlated subqueries
Use the EXISTS and NOT EXISTS operators
Use the WITH clause
Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this lesson, you learn how to write multiple-column subqueries and subqueries in the FROM clause of a
SELECT statement. You also learn how to solve problems by using scalar, correlated subqueries and the
WITH clause.

Introduction to Oracle9i: SQL 18-2

What Is a Subquery?

A subquery is a SELECT statement embedded in a
clause of another SQL statement.

Main
query

SELECT ...
FROM
...
WHERE ...
(SELECT ...
FROM
...
WHERE ...)

18-3

Subquery

Copyright © Oracle Corporation, 2001. All rights reserved.

What Is a Subquery?
A subquery is a SELECT statement that is embedded in a clause of another SQL statement, called the parent
statement.
The subquery (inner query) returns a value that is used by the parent statement. Using a nested subquery is
equivalent to performing two sequential queries and using the result of the inner query as the search value in
the outer query (main query).
Subqueries can be used for the following purposes:
• To provide values for conditions in WHERE, HAVING, and START WITH clauses of SELECT
statements
• To define the set of rows to be inserted into the target table of an INSERT or CREATE TABLE
statement
• To define the set of rows to be included in a view or snapshot in a CREATE VIEW or CREATE
SNAPSHOT statement
• To define one or more values to be assigned to existing rows in an UPDATE statement
• To define a table to be operated on by a containing query. (You do this by placing the subquery in the
FROM clause. This can be done in INSERT, UPDATE, and DELETE statements as well.)
Note: A subquery is evaluated once for the entire parent statement.

Introduction to Oracle9i: SQL 18-3

Subqueries

SELECT select_list
FROM
table
WHERE expr operator (SELECT
FROM

select_list
table);

•

The subquery (inner query) executes once before
the main query.

•

The result of the subquery is used by the main
query (outer query).

18-4

Copyright © Oracle Corporation, 2001. All rights reserved.

Subqueries
You can build powerful statements out of simple ones by using subqueries. Subqueries can be very useful
when you need to select rows from a table with a condition that depends on the data in the table itself or
some other table. Subqueries are very useful for writing SQL statements that need values based on one or
more unknown conditional values.
In the syntax:
operator includes a comparison operator such as >, =, or IN
Note: Comparison operators fall into two classes: single-row operators (>, =, >=, <, <>, <=) and multiplerow operators (IN, ANY, ALL).
The subquery is often referred to as a nested SELECT, sub-SELECT, or inner SELECT statement. The
inner and outer queries can retrieve data from either the same table or different tables.

Introduction to Oracle9i: SQL 18-4

Using a Subquery
SELECT last_name
FROM
employees
10500
WHERE salary >
(SELECT salary
FROM
employees
WHERE employee_id = 149);

18-5

Copyright © Oracle Corporation, 2001. All rights reserved.

Using a Subquery
In the example in the slide, the inner query returns the salary of the employee with employee number 149.
The outer query uses the result of the inner query to display the names of all t he employees who earn more
than this amount.
Example
Display the names of all employees who earn less than the average salary in the company.
SELECT last_name, job_id, salary
FROM
employees
WHERE salary < (SELECT AVG(salary)
FROM
employees);

Introduction to Oracle9i: SQL 18-5

Multiple-Column Subqueries
Main query
WHERE (MANAGER_ID, DEPARTMENT_ID) IN

Subquery
100
102
124

90
60
50

Each row of the main query is compared to
values from a multiple-row and multiple-column
subquery.

18-6

Copyright © Oracle Corporation, 2001. All rights reserved.

Multiple-Column Subqueries
So far you have written single-row subqueries and multiple-row subqueries where only one column is
returned by the inner SELECT statement and this is used to evaluate the expression in the parent select
statement. If you want to compare two or more columns, you must write a compound WHERE clause using
logical operators. Using multiple-column subqueries, you can combine duplicate WHERE conditions into a
single WHERE clause.
Syntax
SELECT
FROM
WHERE

column, column, ...
table
(column, column, ...) IN
(SELECT column, column, ...
FROM
table
WHERE condition);

The graphic in the slide illustrates that the values of the MANAGER_ID and DEPARTMENT_ID from the
main query are being compared with the MANAGER_ID and DEPARTMENT_ID values retrieved by the
subquery. Since the number of columns that are being compared are more than one, the example qualifies
as a multiple-column subquery.

Introduction to Oracle9i: SQL 18-6

Column Comparisons

Column comparisons in a multiple-column subquery
can be:

•
•

18-7

Pairwise comparisons
Nonpairwise comparisons

Copyright © Oracle Corporation, 2001. All rights reserved.

Pairwise Versus Nonpairwise Comparisons
Column comparisons in a multiple-column subquery can be pairwise comparisons or nonpairwise
comparisons.
In the example on the next slide, a pairwise comparison was executed in the WHERE clause. Each candidate
row in the SELECT statement must have both the same MANAGER_ID column and the DEPARTMENT_ID
as the employee with the EMPLOYEE_ID 178 or 174.
A multiple-column subquery can also be a nonpairwise comparison. In a nonpairwise comparison, each of
the columns from the WHERE clause of the parent SELECT statement are individually compared to
multiple values retrieved by the inner select statement. The individual columns can match any of the values
retrieved by the inner select statement. But collectively, all the multiple conditions of the main SELECT
statement must be satisfied for the row to be displayed. The example on the next page illustrates a
nonpairwise comparison.

Introduction to Oracle9i: SQL 18-7

Pairwise Comparison Subquery
Display the details of the employees who are managed
by the same manager and work in the same department
as the employees with EMPLOYEE_ID 178 or 174.

SELECT employee_id, manager_id, department_id
FROM
employees
WHERE (manager_id, department_id) IN
(SELECT manager_id, department_id
FROM
employees
WHERE employee_id IN (178,174))
AND
employee_id NOT IN (178,174);

18-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Pairwise Comparison Subquery
The example in the slide is that of a multiple-column subquery because the subquery returns more than one
column. It compares the values in the MANAGER_ID column and the DEPARTMENT_ID column of each
row in the EMPLOYEES table with the values in the MANAGER_ID column and the DEPARTMENT_ID
column for the employees with the EMPLOYEE_ID 178 or 174.
First, the subquery to retrieve the MANAGER_ID and DEPARTMENT_ID values for the employees with the
EMPLOYEE_ID 178 or 174 is executed. These values are compared with the MANAGER_ID column and the
DEPARTMENT_ID column of each row in the EMPLOYEES table. If the values match, the row is displayed.
In the output, the records of the employees with the EMPLOYEE_ID 178 or 174 will not be displayed. The
output of the query in the slide follows.

Introduction to Oracle9i: SQL 18-8

Nonpairwise Comparison Subquery
Display the details of the employees who are managed by
the same manager as the employees with EMPLOYEE_ID
174 or 141 and work in the same department as the
employees with EMPLOYEE_ID 174 or 141.
SELECT
FROM
WHERE

AND

AND

18-9

employee_id, manager_id, department_id
employees
manager_id IN
(SELECT manager_id
FROM
employees
WHERE employee_id IN (174,141))
department_id IN
(SELECT department_id
FROM
employees
WHERE
employee_id IN (174,141))
employee_id NOT IN(174,141);

Copyright © Oracle Corporation, 2001. All rights reserved.

Nonpairwise Comparison Subquery
The example shows a nonpairwise comparison of the columns. It displays the EMPLOYEE_ID,
MANAGER_ID, and DEPARTMENT_ID of any employee whose manager ID matches any of the manager IDs
of employees whose employee IDs are either 174 or 141 and DEPARTMENT_ID match any of the department
IDs of employees whose employee IDs are either 174 or 141.
First, the subquery to retrieve the MANAGER_ID values for the employees with the EMPLOYEE_ID 174 or
141 is executed. Similarly, the second subquery to retrieve the DEPARTMENT_ID values for the employees
with the EMPLOYEE_ID 174 or 141 is executed. The retrieved values of the MANAGER_ID and
DEPARTMENT_ID columns are compared with the MANAGER_ID and DEPARTMENT_ID column for each
row in the EMPLOYEES table. If the MANAGER_ID column of the row in the EMPLOYEES table matches with
any of the values of the MANAGER_ID retrieved by the inner subquery and if the DEPARTMENT_ID column
of the row in the EMPLOYEES table matches with any of the values of the DEPARTMENT_ID retrieved by
the second subquery, the record is displayed. The output of the query in the slide follows.

Introduction to Oracle9i: SQL 18-9

Using a Subquery
in the FROM Clause
SELECT
FROM

WHERE
AND

18-10

a.last_name, a.salary, a.department_id, b.salavg
employees a, (SELECT
department_id,
AVG(salary) salavg
FROM
employees
GROUP BY department_id) b
a.department_id = b.department_id
a.salary > b.salavg;

Copyright © Oracle Corporation, 2001. All rights reserved.

Using a Subquery in the FROM Clause
You can use a subquery in the FROM clause of a SELECT statement, which is very similar to how views are
used. A subquery in the FROM clause of a SELECT statement is also called an inline view. A subquery in the
FROM clause of a SELECT statement defines a data source for that particular SELECT statement, and only
that SELECT statement. The example on the slide displays employee last names, salaries, department
numbers, and average salaries for all the employees who earn more than the average salary in their
department. The subquery in the FROM clause is named b, and the outer query references the SALAVG column
using this alias.

Introduction to Oracle9i: SQL 18-10

Scalar Subquery Expressions
•

A scalar subquery expression is a subquery that
returns exactly one column value from one row.

•

Scalar subqueries were supported in Oracle8i only in a
limited set of cases, For example :
– SELECT statement (FROM, WHERE clauses)
– VALUES list of an INSERT statement

•

In Oracle9i, scalar subqueries can be used in:
– Condition and expression part of DECODE and CASE
– All clauses of SELECT except GROUP BY

18-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Scalar Subqueries in SQL
A subquery that returns exactly one column value from one row is also referred to as a scalar subquery.
Multiple-column subqueries written to compare two or more columns, using a compound WHERE clause
and logical operators, do not qualify as scalar subqueries.
The value of the scalar subquery expression is the value of the select list item of the subquery. If the
subquery returns 0 rows, the value of the scalar subquery expression is NULL. If the subquery returns more
than one row, the Oracle Server returns an error. The Oracle Server has always supported the usage of a
scalar subquery in a SELECT statement. The usage of scalar subqueries has been enhanced in Oracle9i.
You can now use scalar subqueries in:
• Condition and expression part of DECODE and CASE
• All clauses of SELECT except GROUP BY
• In the left-hand side of the operator in the SET clause and WHERE clause of UPDATE statement
However, scalar subqueries are not valid expressions in the following places:
• As default values for columns and hash expressions for clusters
• In the RETURNING clause of DML statements
• As the basis of a function-based index
• In GROUP BY clauses , CHECK constraints , WHEN conditions
• HAVING clauses
• In START WITH and CONNECT BY clauses
• In statements that are unrelated to queries, such as CREATE PROFILE
Introduction to Oracle9i: SQL 18-11

Scalar Subqueries: Examples
Scalar Subqueries in CASE Expressions
SELECT employee_id, last_name,
(CASE
20
WHEN department_id =
(SELECT department_id FROM departments
WHERE location_id = 1800)
THEN 'Canada' ELSE 'USA' END) location
FROM employees;

Scalar Subqueries in ORDER BY Clause
SELECT employee_id, last_name
FROM employees e
ORDER BY (SELECT department_name
FROM departments d
WHERE e.department_id = d.department_id);

18-12

Copyright © Oracle Corporation, 2001. All rights reserved.

Scalar Subqueries: Examples
The first example in the slide demonstrates that scalar subqueries can be used in CASE expressions. The
inner query returns the value 20, which is the department ID of the department whose location ID is 1800.
The CASE expression in the outer query uses the result of the inner query to display the employee ID, last
names, and a value of Canada or USA, depending on whether the department ID of the record retrieved by
the outer query is 20 or not.
The result of the preceding example follows:

Introduction to Oracle9i: SQL 18-12

Scalar Subqueries: Examples (Continued)
The second example in the slide demonstrates that scalar subqueries can be used in the ORDER BY clause.
The example orders the output based on the DEPARTMENT_NAME by matching the
DEPARTMENT_ID from the EMPLOYEES table with the DEPARTMENT_ID from the DEPARTMENTS
table. This comparison in done in a scalar subquery in the ORDER BY clause. The result of the the second
example follows:

The second example uses a correlated subquery. In a correlated subquery, the subquery references a column
from a table referred to in the parent statement. Correlated subqueries are explained later in this lesson.

Introduction to Oracle9i: SQL 18-13

Correlated Subqueries

Correlated subqueries are used for row-by-row
processing. Each subquery is executed once for
every row of the outer query.
GET
candidate row from outer query

EXECUTE
inner query using candidate row value

USE
values from inner query to qualify or
disqualify candidate row

18-14

Copyright © Oracle Corporation, 2001. All rights reserved.

Correlated Subqueries
The Oracle Server performs a correlated subquery when the subquery references a column from a table
referred to in the parent statement. A correlated subquery is evaluated once for each row processed by the
parent statement. The parent statement can be a SELECT, UPDATE, or DELETE statement.
Nested Subqueries Versus Correlated Subqueries
With a normal nested subquery, the inner SELECT query runs first and executes once, returning values to
be used by the main query. A correlated subquery, however, executes once for each candidate row
considered by the outer query. In other words, the inner query is driven by the outer query.
Nested Subquery Execution
• The inner query executes first and finds a value.
• The outer query executes once, using the value from the inner query.
Correlated Subquery Execution
• Get a candidate row (fetched by the outer query).
• Execute the inner query using the value of the candidate row.
• Use the values resulting from the inner query to qualify or disqualify the candidate.
• Repeat until no candidate row remains.

Introduction to Oracle9i: SQL 18-14

Correlated Subqueries

SELECT column1, column2, ...
FROM
table1 outer
WHERE column1 operator
(SELECT
FROM
WHERE

colum1, column2
table2
expr1 =
outer .expr2);

The subquery references a column from a table in
the parent query.

18-15

Copyright © Oracle Corporation, 2001. All rights reserved.

Correlated Subqueries (continued)
A correlated subquery is one way of reading every row in a table and comparing values in each row
against related data. It is used whenever a subquery must return a different result or set of results for each
candidate row considered by the main query. In other words, you use a correlated subquery to answer a
multipart question whose answer depends on the value in each row processed by the parent statement.
The Oracle Server performs a correlated subquery when the subquery references a column from a table in
the parent query.
Note: You can use the ANY and ALL operators in a correlated subquery.

Introduction to Oracle9i: SQL 18-15

Using Correlated Subqueries
Find all employees who earn more than the average
salary in their department.
SELECT last_name, salary, department_id
FROM
employees outer
WHERE salary > (SELECT AVG(salary)
FROM
employees
WHERE department_id =
outer.department_id);
Each time a row from
the outer query
is processed, the
inner query is
evaluated.

18-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Using Correlated Subqueries (continued)
The example in the slide determines which employees earn more than the average salary of their
department. In this case, the correlated subquery specifically computes the average salary for each
department.
Because both the outer query and inner query use the EMPLOYEES table in the FROM clause, an alias is
given to EMPLOYEES in the outer SELECT statement, for clarity. Not only does the alias make the entire
SELECT statement more readable, but without the alias the query would not work properly, because the
inner statement would not be able to distinguish the inner table column from the outer table column.

Introduction to Oracle9i: SQL 18-16

Using Correlated Subqueries
Display details of those employees who have switched
jobs at least twice.
SELECT e.employee_id, last_name,e.job_id
FROM
employees e
WHERE 2 <= (SELECT COUNT(*)
FROM
job_history
WHERE employee_id = e.employee_id);

18-17

Copyright © Oracle Corporation, 2001. All rights reserved.

Using Correlated Subqueries
The example in the slide displays the details of those employees who have switched jobs at least twice.
The Oracle Server evaluates a correlated subquery as follows:
1. Select a row from the table specified in the outer query. This will be the current candidate row.
2. Store the value of the column referenced in the subquery from this candidate row. (In the example in
the slide, the column referenced in the subquery is E.EMPLOYEE_ID.)
3. Perform the subquery with its condition referencing the value from the outer query’s candidate row.
(In the example in the slide, group function COUNT(*) is evaluated based on the value
of the E.EMPLOYEE_ID column obtained in step 2.)
4. Evaluate the WHERE clause of the outer query on the basis of results of the subquery
performed in step 3. This is determines if the candidate row is selected for output. (In the
example, the number of times an employee has switched jobs, evaluated by the subquery, is
compared with 2 in the WHERE clause of the outer query. If the condition is satisfied, that
employee record is displayed.)
5. Repeat the procedure for the next candidate row of the table, and so on until all the rows in the table
have been processed.
The correlation is established by using an element from the outer query in the subquery. In this
example, the correlation is established by the statement EMPLOYEE_ID = E.EMPLOYEE_ID in
which you compare EMPLOYEE_ID from the table in the subquery with the EMPLOYEE_ID from the
table in the outer query.
Introduction to Oracle9i: SQL 18-17

Using the EXISTS Operator
•

The EXISTS operator tests for existence of rows in
the results set of the subquery.

•

If a subquery row value is found:
– The search does not continue in the inner query
– The condition is flagged TRUE

•

If a subquery row value is not found:
– The condition is flagged FALSE
– The search continues in the inner query

18-18

Copyright © Oracle Corporation, 2001. All rights reserved.

The EXISTS Operator
With nesting SELECT statements, all logical operators are valid. In addition, you can use the EXISTS
operator. This operator is frequently used with correlated subqueries to test whether a value retrieved by
the outer query exists in the results set of the values retrieve d by the inner query. If the subquery returns
at least one row, the operator returns TRUE. If the value does not exist, it returns FALSE. Accordingly,
NOT EXISTS tests whether a value retrieved by the outer query is not a part of the results set of the
values retrieved by the inner query.

Introduction to Oracle9i: SQL 18-18

Using the EXISTS Operator
Find employees who have at least one person
reporting to them.
SELECT employee_id, last_name, job_id, department_id
FROM
employees outer
WHERE EXISTS ( SELECT 'X'
FROM
employees
WHERE manager_id =
outer.employee_id);

18-19

Copyright © Oracle Corporation, 2001. All rights reserved.

Using the EXISTS Operator
The EXISTS operator ensures that the search in the inner query does not continue whe n at least one match
is found for the manager and employee number by the condition:
WHERE manager_id = outer.employee_id.
Note that the inner SELECT query does not need to return a specific value, so a constant can be selected.
From a performance standpoint, it is faster to select a constant than a column.
Note: Having EMPLOYEE_ID in the SELECT clause of the inner query causes a table scan for that
column. Replacing it with the literal X, or any constant, improves performance. This is more efficient than
using the IN operator.
A IN construct can be used as an alternative for a EXISTS operator, as shown in the following example:
SELECT employee_id,last_name,job_id,department_id
FROM
employees
WHERE employee_id IN (SELECT manager_id
FROM
employees
WHERE manager_id IS NOT NULL);

Introduction to Oracle9i: SQL 18-19

Using the NOT EXISTS Operator
Find all departments that do not have any employees.
SELECT department_id, department_name
FROM departments d
WHERE NOT EXISTS (SELECT 'X'
FROM
employees
WHERE department_id
= d.department_id);

18-20

Copyright © Oracle Corporation, 2001. All rights reserved.

Using the NOT EXISTS Operator
Alternative Solution
A NOT IN construct can be used as an alternative for a NOT EXISTS operator, as shown in the following
example.
SELECT department_id, department_name
FROM
departments
WHERE department_id NOT IN (SELECT department_id
FROM
employees);

However, NOT IN evaluates to FALSE if any member of the set is a NULL value. Therefore, your query
will not return any rows even if there are rows in the departmen ts table that satisfy the WHERE condition.

Introduction to Oracle9i: SQL 18-20

Correlated UPDATE
UPDATE table1 alias1
SET
column = (SELECT expression
FROM
table2 alias2
WHERE alias1.column =
alias2.column);

Use a correlated subquery to update rows in one
table based on rows from another table.

18-21

Copyright © Oracle Corporation, 2001. All rights reserved.

Correlated UPDATE
In the case of the UPDATE statement, you can use a correlated subquery to update rows in one table based
on rows from another table.

Introduction to Oracle9i: SQL 18-21

Correlated UPDATE
• Denormalize the EMPLOYEES table by adding a
column to store the department name.
• Populate the table by using a correlated
update.
ALTER TABLE employees
ADD(department_name VARCHAR2(14));

UPDATE employees e
SET department_name =
(SELECT department_name
FROM
departments d
WHERE e.department_id = d.department_id);

18-22

Copyright © Oracle Corporation, 2001. All rights reserved.

Correlated UPDATE (continued)
The example in the slide denormalizes the EMPLOYEES table by adding a column to store the department
name and then populates the table by using a correlated update.
Here is another example for a correlated update.
Problem Statement
Use a correlated subquery to update rows in the EMPLOYEES table based on rows from the REWARDS
table:
UPDATE employees
SET salary = (SELECT employees.salary + rewards.pay_raise
FROM
rewards
WHERE employee_id =
employees.employee_id
AND
payraise_date =
(SELECT MAX(payraise_date)
FROM
rewards
WHERE
employee_id = employees.employee_id))
WHERE employees.employee_id
IN (SELECT employee_id FROM rewards);

Introduction to Oracle9i: SQL 18-22

Correlated UPDATE (continued)
This example uses the REWARDS table. The REWARDS table has the columns EMPLOYEE_ID,
PAY_RAISE, and PAYRAISE_DATE. Every time an employee gets a pay raise, a record with the details
of the employee ID, the amount of the pay raise, and the date of receipt of the pay raise is inserted into the
REWARDS table. The REWARDS table can contain more than one record for an employee. The PAYRAISE
_DATE column is used to identify the most recent pay raise received by an employee.
In the example, the SALARY column in the EMPLOYEES table is updated to reflect the latest pay raise
received by the employee. This is done by adding the current salary of the employee with the
corresponding pay raise from the REWARDS table.

Introduction to Oracle9i: SQL 18-23

Correlated DELETE

DELETE FROM table1 alias1
WHERE column operator
(SELECT expression
FROM
table2 alias2
WHERE alias1.column = alias2.column);

Use a correlated subquery to delete rows in one table
based on rows from another table.

18-24

Copyright © Oracle Corporation, 2001. All rights reserved.

Correlated DELETE
In the case of a DELETE statement, you can use a correlated subquery to delete only those rows that also
exist in another table. If you decide that you will maintain only the last four job hist ory records in the
JOB_HISTORY table, then when an employee transfers to a fifth job, you delete the oldest
JOB_HISTORY row by looking up the JOB_HISTORY table for the MIN(START_DATE)for the
employee. The following code illustrates how the preceding operation can be performed using a correlated
DELETE:
DELETE FROM job_history JH
WHERE employee_id =
(SELECT employee_id
FROM employees E
WHERE JH.employee_id = E.employee_id
AND START_DATE =
(SELECT MIN(start_date)
FROM job_history JH
WHERE JH.employee_id = E.employee_id)
AND 5 > (SELECT COUNT(*)
FROM job_history JH
WHERE JH.employee_id = E.employee_id
GROUP BY EMPLOYEE_ID
HAVING COUNT(*) >= 4));

Introduction to Oracle9i: SQL 18-24

Correlated DELETE
Use a correlated subquery to delete only those rows
from the EMPLOYEES table that also exist in the
EMP_HISTORY table.
DELETE FROM employees E
WHERE employee_id =
(SELECT employee_id
FROM
emp_history
WHERE employee_id = E.employee_id);

18-25

Copyright © Oracle Corporation, 2001. All rights reserved.

Correlated DELETE (continued)
Example
Two tables are used in this example. They are:
• The EMPLOYEES table, which gives details of all the current employees
• The EMP_HISTORY table, which gives details of previous employees
EMP_HISTORY contains data regarding previous employees, so it would be erroneous if the same
employee’s record existed in both the EMPLOYEES and EMP_HISTORY tables. You can delete such
erroneous records by using the correlated subquery shown in the slide.

Introduction to Oracle9i: SQL 18-25

The WITH Clause
•
•
•

Using the WITH clause, you can use the same
query block in a SELECT statement when it occurs
more than once within a complex query.
The WITH clause retrieves the results of a query
block and stores it in the user's temporary
tablespace.
The WITH clause improves performance

18-26

Copyright © Oracle Corporation, 2001. All rights reserved.

The WITH clause
Using the WITH clause, you can define a query block before using it in a query. The WITH clause
(formally known as subquery_factoring_clause) enables you to reuse the same query block in a
SELECT statement when it occurs more than once within a complex query. This is particularly useful
when a query has many references to the same query block and there are joins and aggregations.
Using the WITH clause, you can reuse the same query when it is high cost to evaluate the query block and
it occurs more than once within a complex query. Using the WITH clause, the Oracle Server retrieves the
results of a query block and stores it in the user’s temporary tablespace. This can improve performance.
WITH Clause Benefits
• Makes the query easy to read
• Evaluates a clause only once, even if it appears multiple times in the query, thereby
enhancing performance

Introduction to Oracle9i: SQL 18-26

WITH Clause: Example

Using the WITH clause, write a query to display the
department name and total salaries for those
departments whose total salary is greater than the
average salary across departments.

18-27

Copyright © Oracle Corporation, 2001. All rights reserved.

WITH Clause: Example
The problem in the slide would require the following intermediate calculations:
1. Calculate the total salary for every department, and store the result using a WITH clause.
2. Calculate the average salary across departments, and store the result using a WITH clause.
3. Compare the total salary calculated in the first step with the a verage salary calculated in the second
step. If the total salary for a particular department is greater than the average salary across
departments, display the department name and the total salary for that department.
The solution for the preceding problem is given in the next page.

Introduction to Oracle9i: SQL 18-27

WITH Clause: Example
WITH
dept_costs AS (
SELECT department_name, SUM(salary) AS dept_total
FROM employees, departments
WHERE employees.department_id =
departments.department_id
GROUP BY department_name),
avg_cost AS
(SELECT SUM(dept_total)/COUNT(*) AS dept_avg
FROM dept_costs
)
SELECT * FROM dept_costs
WHERE dept_total >
(SELECT FROM dept_avg )
ORDER BY department_name;

18-28

Copyright © Oracle Corporation, 2001. All rights reserved.

WITH Clause: Example
The SQL code in the slide is an example of a situation in which you can improve performance and write
SQL more simply by using the WITH clause. The query creates the query names DEPT_COSTS and
AVG_COST and then uses them in the body of the main query. Internally, the WITH clause is resolved
either as an in-line view or a temporary table. The optimizer chooses the appropriate resolution depending
on the cost or benefit of temporarily storing the results of the WITH clause.
Note: A subquery in the FROM clause of a SELECT statement is also called an in-line view.
The output generated by the SQL code on the slide will be as follows:
DEPARTMENT_NAME
DEPT_TOTAL
------------------------------ ---------Executive
58000
Sales
37100
The WITH Clause Usage Notes
• It is used only with SELECT statements.
• A query name is visible to all WITH element query blocks (including their subquery blocks) defined
after it and the main query block itself (including its subquery blocks).
• When the query name is the same as an existing table name, the parser searches from the inside out,
the query block name takes precedence over the table name.
• The WITH clause can hold more than one query. Each query is then separated by a comma.

Introduction to Oracle9i: SQL 18-28

Summary

In this lesson, you should have learned the following:

18-29

•

A multiple-column subquery returns more than
one column.

•

Multiple-column comparisons can be pairwise or
nonpairwise.

•

A multiple-column subquery can also be used in
the FROM clause of a SELECT statement.

•

Scalar subqueries have been enhanced in
Oracle 9i.

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
You can use multiple-column subqueries to combine multiple WHERE conditions into a single WHERE
clause. Column comparisons in a multiple-column subquery can be pairwise comparisons or non-pairwise
comparisons.
You can use a subquery to define a table to be operated on by a containing query.
Oracle 9i enhances the the uses of scalar subqueries. Scalar subqueries can now be used in:
• Condition and expression part of DECODE and CASE
• All clauses of SELECT except GROUP BY
• SET clause and WHERE clause of UPDATE statement

Introduction to Oracle9i: SQL 18-29

Summary
•
•
•
•

18-30

Correlated subqueries are useful whenever a
subquery must return a different result for each
candidate row.
The EXISTS operator is a Boolean operator that
tests the presence of a value.
Correlated subqueries can be used with SELECT,
UPDATE, and DELETE statements.
You can use the WITH clause to use the same
query block in a SELECT statement when it occurs
more than once

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
The Oracle Server performs a correlated subquery when the subquery references a column from a table
referred to in the parent statement. A correlated subquery is evaluated once for each row processed by the
parent statement. The parent statement can be a SELECT, UPDATE, or DELETE statement. Using the
WITH clause, you can reuse the same query when it is costly to reevaluate the query block and it occurs
more than once within a complex query.

Introduction to Oracle9i: SQL 18-30

Practice 18 Overview

This practice covers the following topics:

•
•
•
•
•

Creating multiple-column subqueries
Writing correlated subqueries
Using the EXISTS operator
Using scalar subqueries
Using the WITH clause

18-31

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 18 Overview
In this practice, you write multiple-column subqueries, correlated and scalar subqueries. You also solve
problems by writing the WITH clause.

Introduction to Oracle9i: SQL 18-31

Practice 18
1. Write a query to display the last name, department number, and salary of any employee whose
department number and salary both match the department number and salary of any employee
who earns a commission.

2. Display the last name, department name, and salary of any employee whose salary and
commission match the salary and commission of any employee located in location ID 1700.

3. Create a query to display the last name, hire date, and salary for all employees who have the
same salary and commission as Kochhar.
Note: Do not display Kochhar in the result set.

4. Create a query to display the employees who earn a salary that is higher than the salary of
all of the sales managers (JOB_ID = 'SA_MAN'). Sort the results on salary from highest to
lowest.

Introduction to Oracle9i: SQL 18-32

Practice 18 (continued)
5. Display the details of the employee ID, last name, and department ID of those employees who live in
cities whose name begins with T.

6. Write a query to find all employees who earn more than the average salary in their departments.
Display last name, salary, department ID, and the average salary for the department.
Sort by average salary. Use aliases for the columns retrieved by the query as shown in the sample
output.

7. Find all employees who are not supervisors.
a. First do this using the NOT EXISTS operator.

b. Can this be done by using the NOT IN operator? How, or why not?
Introduction to Oracle9i: SQL 18-33

Practice 18 (continued)
8. Write a query to display the last names of the employees who earn less than the average salary in their
departments.

9. Write a query to display the last names of the employees who have one or more coworkers in their
departments with later hire dates but higher salaries.

Introduction to Oracle9i: SQL 18-34

Practice 18 (continued)
10. Write a query to display the employee ID, last names, and department names of all employees.
Note: Use a scalar subquery to retrieve the department name in the SELECT statement.

11. Write a query to display the department names of those departments whose total salary cost is above one
eighth (1/8) of the total salary cost of the whole company. Use the WITH clause to write this query. Name
the query SUMMARY.
DEPARTMENT_NAME
DEPT_TOTAL
------------------------------ ---------Executive
58000
Sales
37100

Introduction to Oracle9i: SQL 18-35

Introduction to Oracle9i: SQL 18-36

Hierarchical Retrieval

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this lesson, you should be able
to do the following:

•
•
•
•

19-2

Interpret the concept of a hierarchical query
Create a tree-structured report
Format hierarchical data
Exclude branches from the tree structure

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this lesson, you learn how to use hierarchical queries to create tree-structured reports.

Introduction to Oracle9i: SQL 19-2

Sample Data from the EMPLOYEES
Table

19-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Sample Data from the EMPLOYEES Table
Using hierarchical queries, you can retrieve data based on a natural hierarchical relationship between rows
in a table. A relational database does not store records in a hierarchical way. However, where a hierarchical
relationship exists between the rows of a single table, a process called tree walking enables the hierarchy to
be constructed. A hierarchical query is a method of reporting, in order, the branches of a tree.
Imagine a family tree with the eldest members of the family foun d close to the base or trunk of the tree and
the youngest members representing branches of the tree. Branches can have their own branches, and so on.
A hierarchical query is possible when a relationship exists betw een rows in a table. For example, in the
slide, you see that employees with the job IDs of AD_VP, ST_MAN, SA_MAN, and MK_MAN report directly
to the president of the company. We know this because the MANAGER_ID column of these records contain
the employee ID 100, which belongs to the president (AD_PRES).
Note: Hierarchical trees are used in various fields such as human genealogy (family trees), livestock
(breeding purposes), corporate management (management hierarchies), manufacturing (product assembly),
evolutionary research (species development), and scientific research.

Introduction to Oracle9i: SQL 19-3

Natural Tree Structure
EMPLOYEE_ID = 100 (Parent)
King

MANAGER_ID = 100 (Child)

Kochhar

Whalen

Higgens

De Hann

Hunold

Mourgos

Rajs Davies

Matos

Zlotkey

Hartstein

Vargas
Goyal

Gietz Ernst

19-4

Abel

Taylor

Grant

Lorentz

Copyright © Oracle Corporation, 2001. All rights reserved.

Natural Tree Structure
The EMPLOYEES table has a tree structure representing the management reporting line. The hierarchy can
be created by looking at the relationship between equivalent values in the EMPLOYEE_ID and
MANAGER_ID columns. This relationship can be exploited by joining the table to itself. The
MANAGER_ID column contains the employee number of the employee’s manager.
The parent-child relationship of a tree structure enables you to control:
• The direction in which the hierarchy is walked
• The starting point inside the hierarchy
Note: The slide displays an inverted tree structure of the management hierarchy of the employees in the
EMPLOYEES table.

Introduction to Oracle9i: SQL 19-4

Hierarchical Queries

SELECT [LEVEL], column, expr...
FROM
table
[WHERE condition(s)]
[START WITH condition(s)]
[CONNECT BY PRIOR condition(s)];

WHERE condition:
expr comparison_operator expr

19-5

Copyright © Oracle Corporation, 2001. All rights reserved.

Keywords and Clauses
Hierarchical queries can be identified by the presence of the CONNECT BY and START WITH clauses.
In the syntax:
SELECT

Is the standard SELECT clause.

LEVEL

For each row returned by a hierarchical query, the LEVEL pseudocolumn
returns 1 for a root row, 2 for a child of a root, and so on.

FROM table

Specifies the table, view, or snapshot containing the columns. You can
select from only one table.
Restricts the rows returned by the query without affecting other rows of
the hierarchy.

WHERE
condition
START WITH

Is a comparison with expressions.
Specifies the root rows of the hierarchy (where to start). This clause is
required for a true hierarchical query.

CONNECT BY
PRIOR

Specifies the columns in which the relationship between parent a nd child
rows exist. This clause is required for a hierarchical query.

The SELECT statement cannot contain a join or query from a view that contains a join.

Introduction to Oracle9i: SQL 19-5

Walking the Tree
Starting Point

•
•

Specifies the condition that must be met
Accepts any valid condition

START WITH column1 = value

•

Using the EMPLOYEES table, start with the
employee whose last name is Kochhar.

...START WITH last_name

19-6

=

'Kochhar'

Copyright © Oracle Corporation, 2001. All rights reserved.

Walking the Tree
The row or rows to be used as the root of the tree are determined by the START WITH clause. The START
WITH clause can be used in conjunction with any valid condition.
Examples
Using the EMPLOYEES table, start with King, the president of the company.
... START WITH manager_id IS NULL
Using the EMPLOYEES table, start with employee Kochhar. A START WITH condition can contain a
subquery.
... START WITH employee_id = (SELECT employee_id
FROM
WHERE

employees
last_name = 'Kochhar')

If the START WITH clause is omitted, the tree walk is started with all of the row s in the table as root rows.
If a WHERE clause is used, the walk is started with all the rows that sati sfy the WHERE condition. This no
longer reflects a true hierarchy.
Note: The clauses CONNECT BY PRIOR and START WITH are not ANSI SQL standard.

Introduction to Oracle9i: SQL 19-6

Walking the Tree
CONNECT BY PRIOR column1 = column2

Walk from the top down using the EMPLOYEES
table
... CONNECT BY PRIOR employee_id = manager_id

Direction

19-7

Top down

Column1 = Parent Key
Column2 = Child Key

Bottom up

Column1 = Child Key
Column2 = Parent Key

Copyright © Oracle Corporation, 2001. All rights reserved.

Walking the Tree (continued)
The direction of the query, whether it is from parent to child or from child to parent, is determined by the
CONNECT BY PRIOR column placement. The PRIOR operator refers to the parent row. To find the
children of a parent row, the Oracle Server evaluates the PRIOR expression for the parent row and the
other expressions for each row in the table. Rows for which the condition is true are the children of the
parent. The Oracle Server always selects children by evaluating the CONNECT BY condition with respect
to a current parent row.
Examples
Walk from the top down using the EMPLOYEES table. Define a hierarchical relationship in which the
EMPLOYEE_ID value of the parent row is equal to the MANAGER_ID value of the child row.
... CONNECT BY PRIOR employee_id = manager_id
Walk from the bottom up using the EMPLOYEES table.
... CONNECT BY PRIOR manager_id = employee_id
The PRIOR operator does not necessarily need to be coded immediately following the CONNECT BY.
Thus, the following CONNECT BY PRIOR clause gives the same result as the one in the preceding
example.
... CONNECT BY employee_id = PRIOR manager_id
Note: The CONNECT BY clause cannot contain a subquery.

Introduction to Oracle9i: SQL 19-7

Walking the Tree: From the Bottom Up

SELECT employee_id, last_name, job_id, manager_id
FROM
employees
START WITH employee_id = 101
CONNECT BY PRIOR manager_id = employee_id;

19-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Walking the Tree: From the Bottom Up
The example in the slide displays a list of managers starting with the employee whose employee ID is 101.
Example
In the following example, EMPLOYEE_ID values are evaluated for the parent row and MANAGER_ID, and
SALARY values are evaluated for the child rows. The PRIOR operator applies only to the EMPLOYEE_ID
value.
... CONNECT BY PRIOR employee_id = manager_id
AND salary > 15000;
To qualify as a child row, a row must have a MANAGER_ID value equal to the EMPLOYEE_ID value of
the parent row and must have a SALARY value greater than $15,000.

Introduction to Oracle9i: SQL 19-8

Walking the Tree: From the Top Down
SELECT
PRIOR
FROM
START
CONNECT

19-9

last_name||' reports to '||
last_name "Walk Top Down"
employees
WITH last_name = 'King'
BY PRIOR employee_id = manager_id;

Copyright © Oracle Corporation, 2001. All rights reserved.

Walking the Tree: From the Top Down
Walking from the top down, display the names of the employees and their manager. Use employee King as
the starting point. Print only one column.

Introduction to Oracle9i: SQL 19-9

Ranking Rows with the LEVEL
Pseudocolumn
Level 1
root/parent
King

Kochhar

De Hann

Whalen Higgens Hunold

Level 2
parent/child

Mourgos

Rajs Davies

Matos

Zlotkey

Hartstein
Level 3
parent/child
/leaf

Vargas

Goyal
Gietz Ernst

19-10

Abel

Taylor

Lorentz

Grant

Level 4
leaf

Copyright © Oracle Corporation, 2001. All rights reserved.

Ranking Rows with the LEVEL Pseudocolumn
You can explicitly show the rank or level of a row in the hierarchy by using the LEVEL pseudocolumn.
This will make your report more readable. The forks where one or more branches split away from a larger
branch are called nodes, and the very end of a branch is called a leaf, or leaf node. The diagram in the slide
shows the nodes of the inverted tree with their LEVEL values. For example, employee Higgens is a parent
and a child, while employee Davies is a child and a leaf.
The LEVEL Pseudocolumn

Value
1
2
3

Level
A root node
A child of a root node
A child of a child, and so on

Note: A root node is the highest node within an inverted tree. A child node is any nonroot node. A parent
node is any node that has children. A leaf node is any node without children. The number of levels
returned by a hierarchical query may be limited by available user memory.
In the slide, King is the root or parent (LEVEL = 1). Kochhar, De Hann, Mourgos, Zlotkey, Hartstein,
Higgens, and Hunold are children and also parents (LEVEL = 2). Whalen, Rajs, Davies, Matos, Vargas,
Gietz, Ernst, Lorentz, Abel, Taylor, Grant, and Goyal are children and leaves.
(LEVEL = 3 and LEVEL = 4)

Introduction to Oracle9i: SQL 19-10

Formatting Hierarchical Reports Using
LEVEL and LPAD
Create a report displaying company management
levels, beginning with the highest level and indenting
each of the following levels.
COLUMN org_chart FORMAT A12
SELECT LPAD(last_name, LENGTH(last_name)+(LEVEL*2) -2,'_')
AS org_chart
FROM
employees
START WITH last_name='King'
CONNECT BY PRIOR employee_id=manager_id

19-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Formatting Hierarchical Reports Using LEVEL
The nodes in a tree are assigned level numbers from the root. Use the LPAD function in conjunction with
the pseudocolumn LEVEL to display a hierarchical report as an indented tree.
In the example on the slide:
• LPAD(ciar1,n [,char2]) returns char1, left-padded to length n with the sequence of
characters in char2. The argument n is the total length of the return value as it is displayed on your
terminal screen.
• LPAD(last_name, LENGTH(last_name)+(LEVEL*2) -2,'_')defines the display
format.
• char1 is the LAST_NAME , n the total length of the return value, is length of the LAST_NAME
+(LEVEL*2)-2 ,and char2 is '_'.
In other words, this tells SQL to take the LAST_NAME and left-pad it with the '_' character till the
length of the resultant string is equal to the value determined by LENGTH(last_name)+(LEVEL*2)2.
For King, LEVEL = 1. Hence, (2 * 1) - 2 = 2 - 2 = 0. So King does not get padded with any '_'
character and is displayed in column 1.
For Kochhar, LEVEL = 2. Hence, (2 * 2) - 2 = 4 - 2 = 2 . So Kochhar gets padded with 2 '_'
characters and is displayed indented.
The rest of the records in the EMPLOYEES table are displayed similarly.

Introduction to Oracle9i: SQL 19-11

Formatting Hierarchical Reports Using LEVEL (continued)

Introduction to Oracle9i: SQL 19-12

Pruning Branches
Use the WHERE clause
to eliminate a node.
WHERE last_name != 'Higgins'
Kochhar

Use the CONNECT BY clause
to eliminate a branch.
CONNECT BY PRIOR
employee_id = manager_id
AND last_name != 'Higgins'
Kochhar

Whalen

Higgins
Whalen

Higgins

Gietz
Gietz

19-13

Copyright © Oracle Corporation, 2001. All rights reserved.

Pruning Branches
You can use the WHERE and CONNECT BY clauses to prune the tree; that is, to control which nodes or
rows are displayed. The predicate you use acts as a Boolean condition.
Examples
Starting at the root, walk from the top down, and eliminate employee Higgins in the result, but process the
child rows.
SELECT department_id, employee_id,last_name, job_id, salar y
FROM
employees
WHERE
last_name != 'Higgins'
START
WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id;
Starting at the root, walk from the top down, and eliminate employee Higgins and all child rows.
SELECT department_id, employee_id,last_name, job_id, salary
FROM
employees
START WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id
AND last_name != 'Higgins';

Introduction to Oracle9i: SQL 19-13

Summary

In this lesson, you should have learned the following:

•

You can use hierarchical queries to view a
hierarchical relationship between rows in a table.

•

You specify the direction and starting point of
the query.

•

You can eliminate nodes or branches by pruning.

19-14

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
You can use hierarchical queries to retrieve data based on a natural hierarchical relationship between rows
in a table. The LEVEL pseudocolumn counts how far down a hierarchical tree you have traveled. You can
specify the direction of the query using the CONNECT BY PRIOR clause. You can specify the starting
point using the START WITH clause. You can use the WHERE and CONNECT BY clauses to prune the
tree branches.

Introduction to Oracle9i: SQL 19-14

Practice 19 Overview

This practice covers the following topics:

•

Distinguishing hierarchical queries from
nonhierarchical queries

•
•

Performing tree walks
Producing an indented report by using the LEVEL
pseudocolumn

•
•

Pruning the tree structure
Sorting the output

19-15

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 19 Overview
In this practice, you gain practical experience in producing hierarchical reports.
Paper-Based Questions
Question 1 is a paper-based question.

Introduction to Oracle9i: SQL 19-15

Practice 19
1. Look at the following output. Is this output the result of a hierarchical query? Explain why or why not.
a. Exhibit 1:

Exhibit 2:

Exhibit 3:

Introduction to Oracle9i: SQL 19-16

Practice 19 (continued)
Exhibit 3:

Introduction to Oracle9i: SQL 19-17

Practice 19 (continued)
2. Produce a report showing an organization chart for Mourgos’s department. Print last names, salaries,
and department IDs.

3. Create a report that shows the hierarchy of the managers for the employee Lorentz. Display his
immediate manager first.

Introduction to Oracle9i: SQL 19-18

Practice 19 (continued)
4.

Create an indented report showing the management hierarchy starting from the employee whose
LAST_NAME is Kochhar. Print the employee’s last name, manager ID, and department ID. Give
alias names to the columns as shown in the sample output.

If you have time, complete the following exercise:
5.

Produce a company organization chart that shows the management hierarchy. Start with the person
at the top level, exclude all people with a job ID of IT_PROG, and exclude De Haan and those
employees who report to De Haan.

Introduction to Oracle9i: SQL 19-19

Introduction to Oracle9i: SQL 19-20

Oracle 9i Extensions to
DML and DDL Statements

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this lesson, you should be able to
do the following:

•
•

Describe the features of multitable inserts
Use the following types of multitable inserts
–
–
–
–

•
•

20-2

Unconditional INSERT
Pivoting INSERT
Conditional ALL INSERT
Conditional FIRST INSERT

Create and use external tables
Name the index at the time of creating a primary
key constraint
Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
This lesson addresses the Oracle9i extensions to DDL and DML statements. It focuses on multitable
INSERT statements, types of multitable INSERT statements, external tables, and the provision to name the
index at the time of creating a primary key constraint.

Introduction to Oracle9i: SQL 20-2

Review of the INSERT Statement
•

Add new rows to a table by using the INSERT
statement.

INSERT INTO
VALUES

•

table [(column [, column...])]
(value [, value...]);

Only one row is inserted at a time with this syntax.

INSERT INTO departments(department_id, department_name,
manager_id, location_id)
VALUES
(70, 'Public Relations', 100, 1700);
1 row created.

20-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Review of the INSERT Statement
You can add new rows to a table by issuing the INSERT statement.
In the syntax:
table

is the name of the table

column

is the name of the column in the table to populate

value

is the corresponding value for the column

Note: This statement with the VALUES clause adds only one row at a time to a table.

Introduction to Oracle9i: SQL 20-3

Review of the UPDATE Statement
•

Modify existing rows with the UPDATE statement.

UPDATE
SET
[WHERE

•
•

table
column = value [, column = value, ...]
condition];

Update more than one row at a time, if required.
Specific row or rows are modified if you specify
the WHERE clause.

UPDATE employees
SET
department_id = 70
WHERE employee_id = 142;
1 row updated.

20-4

Copyright © Oracle Corporation, 2001. All rights reserved.

Review of the UPDATE Statement
You can modify existing rows by using the UPDATE statement.
In the syntax:
table

is the name of the table

column

is the name of the column in the table to populate

value

is the corresponding value or subquery for the column

condition

identifies the rows to be updated and is composed of column names
expressions, constants, subqueries, and comparison operators

Confirm the update operation by querying the table to display the updated rows.

Introduction to Oracle9i: SQL 20-4

Overview of Multitable INSERT Statements
•
•
•

The INSERT…SELECT statement can be used to
insert rows into multiple tables as part of a single
DML statement.
Multitable INSERT statements can be used in data
warehousing systems to transfer data from one or
more operational sources to a set of target tables.
They provide significant performance
improvement over:
– Single DML versus multiple INSERT.. SELECT
statements
– Single DML versus a procedure to do multiple
inserts using IF...THEN syntax

20-5

Copyright © Oracle Corporation, 2001. All rights reserved.

Overview of Multitable INSERT Statements
In a multitable INSERT statement, you insert computed rows derived from the rows returned from the
evaluation of a subquery into one or more tables.
Multitable INSERT statements can play a very useful role in a data warehouse scenario. You need to load
your data warehouse regularly so that it can serve its purpose of facilitating business analysis. To do this,
data from one or more operational systems needs to be extracted and copied into the warehouse. The
process of extracting data from the source system and bringing it into the data warehouse is commonly
called ETL, which stands for extraction, transformation, and loading.
During extraction, the desired data has to be identified and extracted from many different sources, such as
database systems and applications. After extraction, the data has to be physically transported to the target
system or an intermediate system for further processing. Depending on the chosen way of transportation,
some transformations can be done during this process. For example, a SQL statement that directly accesses
a remote target through a gateway can concatenate two columns as part of the SELECT statement.
Once data is loaded into an Oracle9i, database, data transformations can be executed using SQL
operations. With Oracle9i multitable INSERT statements is one of the techniques for implementing SQL
data transformations.

Introduction to Oracle9i: SQL 20-5

Overview of Multitable Insert Statements
Multitable INSERTS statement offer the benefits of the INSERT ... SELECT statement when multiple
tables are involved as targets. Using functionality prior to Oracle9i, you had to deal with n independent
INSERT ... SELECT statements, thus processing the same source data n times and increasing the
transformation workload n times.
As with the existing INSERT ... SELECT statement, the new statement can be parallelized and used
with the direct-load mechanism for faster performance.
Each record from any input stream, such as a nonrelational database table, can now be converted into
multiple records for more relational database table environment. To implement this functionality before
Oracle9i, you had to write multiple INSERT statements.

Introduction to Oracle9i: SQL 20-6

Types of Multitable INSERT Statements
Oracle9i introduces the following types of multitable insert
statements:
•

Unconditional INSERT

•

Conditional ALL INSERT

•

Conditional FIRST INSERT

•

Pivoting INSERT

20-7

Copyright © Oracle Corporation, 2001. All rights reserved.

Types of Multitable INSERT Statements
Oracle 9i introduces the following types of multitable INSERT statements:
•

Unconditional INSERT

•

Conditional ALL INSERT

•

Conditional FIRST INSERT

•

Pivoting INSERT

You use different clauses to indicate the type of INSERT to be executed.

Introduction to Oracle9i: SQL 20-7

Multitable INSERT Statements
Syntax
INSERT [ALL] [conditional_insert_clause]
[insert_into_clause values_clause] (subquery)

conditional_insert_clause
[ALL] [FIRST]
[WHEN condition THEN] [insert_into_clause values_clause]
[ELSE] [insert_into_clause values_clause]

20-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Multitable INSERT Statements
The slide displays the generic format for multitable INSERT statements. There are four types of multitable
insert statements.
•

Unconditional INSERT

•

Conditional ALL INSERT

•

Conditional FIRST INSERT

•

Pivoting INSERT

Unconditional INSERT: ALL into_clause
Specify ALL followed by multiple insert_into_clauses to perform an unconditional multitable
insert. The Oracle Server executes each insert_into_clause once for each row returned by the
subquery.
Conditional INSERT: conditional_insert_clause
Specify the conditional_insert_clause to perform a conditional multitable insert. The Oracle
server filters each insert_into_clause through the corresponding WHEN condition, which
determines whether that insert_into_clause is executed. A single multitable insert statement can
contain up to 127 WHEN clauses.
Conditional INSERT: ALL
If you specify ALL, the Oracle server evaluates each WHEN clause regardless of the results of the
evaluation of any other WHEN clause. For each WHEN clause whose condition evaluates to true, the Oracle
server executes the corresponding INTO clause list.
Introduction to Oracle9i: SQL 20-8

Multitable INSERT Statements (continued)
Conditional FIRST: INSERT
If you specify FIRST, the Oracle Server evaluates each WHEN clause in the order in which it appears in the
statement. If the first WHEN clause evaluates to true, the Oracle Server executes the corresponding INTO
clause and skips subsequent WHEN clauses for the given row.
Conditional INSERT: ELSE Clause
For a given row, if no WHEN clause evaluates to true:
•

If you have specified an ELSE, clause the Oracle Server executes the INTO clause list associated
with the ELSE clause.

•

If you did not specify an ELSE clause, the Oracle Server takes no action for that row.

Restrictions on Multitable INSERT Statements
•

You can perform multitable inserts only on tables, not on views or materialized views.

•

You cannot perform a multitable insert into a remote table.

•
•

You cannot specify a table collection expression when performing a multitable insert.
In a multitable insert, all of the insert_into_clauses cannot combine to specify more than
999 target columns.

Introduction to Oracle9i: SQL 20-9

Unconditional INSERT ALL
•

•

Select the EMPLOYEE_ID, HIRE_DATE, SALARY, and
MANAGER_ID values from the EMPLOYEES table for
those employees whose EMPLOYEE_ID is greater
than 200.
Insert these values into the SAL_HISTORY and
MGR_HISTORY tables using a multitable INSERT.

INSERT ALL
INTO sal_history VALUES(EMPID,HIREDATE,SAL)
INTO mgr_history VALUES(EMPID,MGR,SAL)
SELECT employee_id EMPID ,hire_date HIREDATE ,
salary SAL , manager_id MGR
FROM employees
WHERE employee_id > 200;

20-10

Copyright © Oracle Corporation, 2001. All rights reserved.

Unconditional INSERT ALL
The example in the slide inserts rows into both the SAL_HISTORY and the MGR_HISTORY tables.
The SELECT statement retrieves the details of employee ID, hire date, salary, and manager ID of those
employees whose employee ID is greater than 200 from the EMPLOYEES table. The details of the
employee ID, hire date, and salary are inserted into the SAL_HISTORY table. The details of employee ID,
manager ID and salary are inserted into the MGR_HISTORY table.
This INSERT statement is referred to as an unconditional INSERT, as no further restriction is applied to
the rows that are retrieved by the SELECT statement. All the rows retrieved by the SELECT statement are
inserted into the two tables, SAL_HISTORY and MGR_HISTORY. The VALUES clause in the INSERT
statements specifies the columns from the SELECT statement that have to be inserted into each of the
tables. Each row returned by the SELECT statement results in two inserts, one for the SAL_HISTORY
table and one for the MGR_HISTORY table.
The feedback 8 rows created can be interpreted to mean that a total of eight inserts were performed
on the base tables, SAL_HISTORY and MGR_HISTORY.

Introduction to Oracle9i: SQL 20-10

Conditional INSERT ALL
•

•
•

Select the EMPLOYEE_ID, HIRE_DATE, SALARY and
MANAGER_ID values from the EMPLOYEES table for
those employees whose EMPLOYEE_ID is greater
than 200.
If the SALARY is greater than $10,000, insert these
values into the SAL_HISTORY table using a
conditional multitable INSERT statement.
If the MANAGER_ID is greater than 200, insert these
values into the MGR_HISTORY table using a
conditional multitable INSERT statement.

20-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Conditional INSERT ALL
The problem statement for a conditional INSERT ALL statement is specified in the slide. The solution to
the preceding problem is shown in the next page.

Introduction to Oracle9i: SQL 20-11

Conditional INSERT ALL
INSERT ALL
WHEN SAL > 10000 THEN
INTO sal_history VALUES(EMPID,HIREDATE,SAL)
WHEN MGR > 200 THEN
INTO mgr_history VALUES(EMPID,MGR,SAL)
SELECT employee_id EMPID ,hire_date HIREDATE ,
salary SAL , manager_id MGR
FROM employees
WHERE employee_id > 200;
4 rows created.

20-12

Copyright © Oracle Corporation, 2001. All rights reserved.

Conditional INSERT ALL (continued)
The example on the slide is similar to the example on the previous slide as it inserts rows into both the
SAL_HISTORY and the MGR_HISTORY tables. The SELECT statement retrieves the details of employee
ID, hire date, salary, and manager ID of those employees whose employee ID is greater than 200 from the
EMPLOYEES table. The details of employee ID, hire date, and salary are inserted into the SAL_HISTORY
table. The details of employee ID, manager ID, and salary are inserted into the MGR_HISTORY table.
This INSERT statement is referred to as a conditional ALL INSERT, as a further restriction is applied to
the rows that are retrieved by the SELECT statement. From the rows that are retrieved by the SELECT
statement, only those rows in which the value of the SAL column is more than 10000 are inserted in the
SAL_HISTORY table, and similarly only those rows where the value of the MGR column is more than 200
are inserted in the MGR_HISTORY table.
Observe that unlike the previous example, where eight rows were inserted into the tables, in this example
only four rows are inserted.
The feedback 4 rows created can be interpreted to mean that a total of four inserts were performed
on the base tables, SAL_HISTORY and MGR_HISTORY.

Introduction to Oracle9i: SQL 20-12

Conditional FIRST INSERT
•

Select the DEPARTMENT_ID , SUM(SALARY) and
MAX(HIRE_DATE) from the EMPLOYEES table.

•

If the SUM(SALARY) is greater than $25,000 then
insert these values into the SPECIAL_SAL, using a
conditional FIRST multitable INSERT.

•

If the first WHEN clause evaluates to true, the
subsequent WHEN clauses for this row should be
skipped.
For the rows that do not satisfy the first WHEN
condition, insert into the HIREDATE_HISTORY_00,
or HIREDATE_HISTORY_99, or HIREDATE_HISTORY
tables, based on the value in the HIRE_DATE
column using a conditional multitable INSERT.

•

20-13

Copyright © Oracle Corporation, 2001. All rights reserved.

Conditional FIRST INSERT
The problem statement for a conditional FIRST INSERT statement is specified in the slide. The solution
to the preceding problem is shown on the next page.

Introduction to Oracle9i: SQL 20-13

Conditional FIRST INSERT
INSERT FIRST
WHEN SAL > 25000 THEN
INTO special_sal VALUES(DEPTID, SAL)
WHEN HIREDATE like ('%00%') THEN
INTO hiredate_history_00 VALUES(DEPTID,HIREDATE)
WHEN HIREDATE like ('%99%') THEN
INTO hiredate_history_99 VALUES(DEPTID, HIREDATE)
ELSE
INTO hiredate_history VALUES(DEPTID, HIREDATE)
SELECT department_id DEPTID, SUM(salary) SAL,
MAX(hire_date) HIREDATE
FROM employees
GROUP BY department_id;

20-14

Copyright © Oracle Corporation, 2001. All rights reserved.

Conditional FIRST INSERT (continued)
The example in the slide inserts rows into more than one table, using one single INSERT statement. The
SELECT statement retrieves the details of department ID, total salary, and maximum hire date for every
department in the EMPLOYEES table.
This INSERT statement is referred to as a conditional FIRST INSERT, as an exception is made for the
departments whose total salary is more than $25,000. The condition WHEN ALL > 25000 is evaluated
first. If the total salary for a department is more than $25,000, then the record is inserted into the
SPECIAL_SAL table irrespective of the hire date. If this first WHEN clause evaluates to true, the Oracle
server executes the corresponding INTO clause and skips subsequent WHEN clauses for this row.
For the rows that do not satisfy the first WHEN condition (WHEN SAL > 25000), the rest of the
conditions are evaluated just as a conditional INSERT statement, and the records retrieved by the SELECT
statement are inserted into the HIREDATE_HISTORY_00, or HIREDATE_HISTORY_99, or
HIREDATE_HISTORY tables, based on the value in the HIREDATE column.
The feedback 8 rows created can be interpreted to mean that a total of eight INSERT statements
were performed on the base tables, SPECIAL_SAL ,HIREDATE_HISTORY_00,
HIREDATE_HISTORY_99, and HIREDATE_HISTORY.

Introduction to Oracle9i: SQL 20-14

Pivoting INSERT
•

Suppose you receive a set of sales records from a
nonrelational database table,
SALES_SOURCE_DATA in the following format:
EMPLOYEE_ID, WEEK_ID, SALES_MON,
SALES_TUE, SALES_WED, SALES_THUR,
SALES_FRI

•

You would want to store these records in the
SALES_INFO table in a more typical relational
format:
EMPLOYEE_ID, WEEK, SALES

•

Using a pivoting INSERT, convert the set of sales
records from the nonrelational database table to
relational format.

20-15

Copyright © Oracle Corporation, 2001. All rights reserved.

Pivoting INSERT
Pivoting is an operation in which you need to build a transformation such that each record from any input
stream, such as, a nonrelational database table, must be converted into multiple records for a more
relational database table environment.
In order to solve the problem mentioned in the slide, you need to build a transformation such that each
record from the original nonrelational database table, SALES_SOURCE_DATA, is converted into five
records for the data warehouse's SALES_INFO table. This operation is commonly referred to as pivoting.
The problem statement for a pivoting INSERT statement is specified in the slide. The solution to the
preceding problem is shown in the next page.

Introduction to Oracle9i: SQL 20-15

Pivoting INSERT

INSERT ALL
INTO sales_info VALUES (employee_id,week_id,sales_MON)
INTO sales_info VALUES (employee_id,week_id,sales_TUE)
INTO sales_info VALUES (employee_id,week_id,sales_WED)
INTO sales_info VALUES (employee_id,week_id,sales_THUR)
INTO sales_info VALUES (employee_id,week_id, sales_FRI)
SELECT EMPLOYEE_ID, week_id, sales_MON, sales_TUE,
sales_WED, sales_THUR,sales_FRI
FROM sales_source_data;

20-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Pivoting INSERT
In the example in the slide, the sales data is received from the nonrelational database table
SALES_SOURCE_DATA, which is the details of the sales performed by a sales representative on each day
of a week, for a week with a particular week ID.
DESC SALES_SOURCE_DATA

Introduction to Oracle9i: SQL 20-16

Pivoting INSERT (continued)
SELECT * FROM SALES_SOURCE_DATA;

DESC SALES_INFO

SELECT * FROM sales_info;

Observe in the preceding example that using a pivoting INSERT, one row from the
SALES_SOURCE_DATA table is converted into five records for the relational table, SALES_INFO.

Introduction to Oracle9i: SQL 20-17

External Tables
•

External tables are read-only tables in which the
data is stored outside the database in flat files.

•

The metadata for an external table is created
using a CREATE TABLE statement.

•

With the help of external tables, Oracle data can
be stored or unloaded as flat files.

•

The data can be queried using SQL but you cannot
use DML and no indexes can be created.

20-18

Copyright © Oracle Corporation, 2001. All rights reserved.

External Tables
An external table is a read-only table whose metadata is stored in the database but whose data is stored
outside the database. Using the Oracle9 external table feature, you can use external data as a virtual table.
This data can be queried and joined directly and in parallel without requiring the external data to be first
loaded in the database. You can use SQL, PL/SQL, and Java to query the data in an external table.
The main difference between external tables and regular tables is that externally organized tables are readonly. No DML operations (UPDATE/INSERT/DELETE) are possible, and no indexes can be created on
them.
The means of defining the metadata for external tables is through the CREATE TABLE ...
ORGANIZATION EXTERNAL statement. This external table definition can be thought of as a view that is
used for running any SQL query against external data without requiring that the external data first be
loaded into the database.
The Oracle Server provides two major access drivers for external tables. One, the loader access driver, or
ORACLE_LOADER, is used for reading of data from external files using the Oracle loader technology. This
access driver allows the Oracle Server to access data from any data source whose format can be interpreted
by the SQL*Loader utility. The other Oracle provided access driver, the import/export access driver, or
ORACLE_ INTERNAL, can be used for both the importing and exporting of data using a platform
independent format.

Introduction to Oracle9i: SQL 20-18

Creating an External Table
•

Use the external_table_clause along with the
CREATE TABLE syntax to create an external table.

•

Specify ORGANIZATION as EXTERNAL to indicate
that the table is located outside the database.
The external_table_clause consists of the
access driver TYPE,
external_data_properties, and the REJECT
LIMIT.

•

•

The external_data_properties consist of the
following:
– DEFAULT DIRECTORY
– ACCESS PARAMETERS
– LOCATION

20-19

Copyright © Oracle Corporation, 2001. All rights reserved.

Creating an External Table
You create external tables using the ORGANIZATION EXTERNAL clause of the CREATE TABLE
statement. You are not in fact creating a table. Rather, you are creating metadata in the data dictionary that
you can use to access external data. The ORGANIZATION clause lets you specify the order in which the
data rows of the table are stored. By specifying EXTERNAL in the ORGANIZATION clause, you indicate
that the table is a read-only table located outside the database.
TYPE access_driver_type indicates the access driver of the external table. The access driver is the
Application Programming Interface (API) that interprets the external data for the database. If you do not
specify TYPE, Oracle uses the default access driver, ORACLE_LOADER.
The REJECT LIMIT clause lets you specify how many conversion errors can occur during a query of the
external data before an Oracle error is returned and the query is aborted. The default value is 0.
DEFAULT DIRECTORY lets you specify one or more default directory objects corresponding to
directories on the file system where the external data sources may reside. Default directories can also be
used by the access driver to store auxiliary files such as error logs. Multiple default directories are
permitted to facilitate load balancing on multiple disk drives.
The optional ACCESS PARAMETERS clause lets you assign values to the parameters of the specific
access driver for this external table. Oracle does not interpret anything in this clause. It is up to the access
driver to interpret this information in the context of the external data.
The LOCATION clause lets you specify one external locator for each external data source. Usually the
location_specifier is a file, but it need not be. Oracle does not interpret this clause. It is up to the
access driver to interpret this information in the context of the external data.
Introduction to Oracle9i: SQL 20-19

Example of Creating an External Table

Create a DIRECTORY object that corresponds to the
directoryon the file system where the external data
source resides.
CREATE DIRECTORY emp_dir AS '/flat_files' ;

20-20

Copyright © Oracle Corporation, 2001. All rights reserved.

Example of Creating an External Table
Use the CREATE DIRECTORY statement to create a directory object. A directory object specifies an alias
for a directory on the server's file system where an external data source resides. You can use directory
names when referring to an external data source, rather than hard-code the operating system pathname, for
greater file management flexibility.
You must have CREATE ANY DIRECTORY system privileges to create directories. When you create a
directory, you are automatically granted the READ object privilege and can grant READ privileges to other
users and roles. The DBA can also grant this privilege to other users and roles.
Syntax
CREATE [OR REPLACE] DIRECTORY AS 'path_name';
In the syntax:
OR REPLACE

directory

'path_name'

Specify OR REPLACE to re-create the directory database object if it
already exists. You can use this clause to change the definition of an
existing directory without dropping, re-creating, and regranting database
object privileges previously granted on the directory. Users who had
previously been granted privileges on a redefined directory can still
access the directory without being regranted the privileges
Specify the name of the directory object to be created. The maximum
length of directory is 30 bytes. You cannot qualify a directory object
with a schema name.
Specify the full pathname of the operating system directory on the server where
the files are located. The single quotes are required, with the result that the path
name is case sensitive.
Introduction to Oracle9i: SQL 20-20

Example of Creating an External Table
CREATE TABLE oldemp (
empno NUMBER, empname CHAR(20), birthdate DATE)
ORGANIZATION EXTERNAL
(TYPE ORACLE_LOADER
DEFAULT DIRECTORY emp_dir
ACCESS PARAMETERS
(RECORDS DELIMITED BY NEWLINE
BADFILE 'bad_emp'
LOGFILE 'log_emp'
FIELDS TERMINATED BY ','
(empno CHAR,
empname CHAR,
birthdate CHAR date_format date mask "dd-mon-yyyy"))
LOCATION ('emp1.txt'))
PARALLEL 5
REJECT LIMIT 200;

20-21

Copyright © Oracle Corporation, 2001. All rights reserved.

Example of Creating an External Table (continued)
Assume that there is a flat file that has records in the followi ng format:
10,jones,11-Dec-1934
20,smith,12-Jun-1972
Records are delimited by new lines, and the fields are all terminated by a ",". The name of the file is:
/flat_files/emp1.txt
To convert this file as the data source for an external table, whose metadata will reside in the database, you
need to perform the following steps:
1. Create a directory object emp_dir as follows:
CREATE DIRECTORY emp_dir AS '/flat_files' ;
2. Run the CREATE TABLE command shown in the slide.
The example in the slide illustrates the table specification to create an external table for the file:
/flat_files/emp1.txt
In the example, the TYPE specification is given only to illustrate its use. If not specified,
ORACLE_LOADER is the default access driver. The ACCESS PARAMETERS provide values to parameters
of the specific access driver and are interpreted by the access driver, not by the Oracle Server.
The PARALLEL clause enables five parallel execution servers to simultaneously scan the external data
sources (files) when executing the INSERT INTO TABLE statement. For example, if PARALLEL=5
were specified, then more that one parallel execution server could be working on a data source. Because
external tables can be very large, for performance reasons it is advisable to specify the PARALLEL clause,
or a parallel hint for the query.
Introduction to Oracle9i: SQL 20-21

Example of Defining External Tables (continued)
The REJECT LIMIT clause specifies that if more than 200 conversion errors occur during a query of the
external data, the query is aborted and an error returned. These conversion errors can arise when the access
driver tries to transform the data in the data file to match the external table definition.
Once the CREATE TABLE command executes successfully, the external table OLDEMP can be described,
queried upon like a relational table.
DESC oldemp

In the following example, the INSERT INTO TABLE statement generates a dataflow from the external
data source to the Oracle SQL engine where data is processed. As data is extracted from the external table,
it is transparently converted by the ORACLE_ LOADER access driver from its external representation into
an equivalent Oracle native representation. The INSERT statement inserts data from the external table
OLDEMP into the BIRTHDAYS table:
INSERT INTO birthdays(empno, empname, birthdate)
SELECT empno, empname, birthdate FROM oldemp;

We can now select from the BIRTHDAYS table.
SELECT * FROM birthdays;

Introduction to Oracle9i: SQL 20-22

Querying External Tables
SELECT *
FROM oldemp

emp1.txt

20-23

Copyright © Oracle Corporation, 2001. All rights reserved.

Querying External Table
An external table does not describe any data that is stored in the database. Nor does it describe how data is
stored in the external source. Instead, it describes how the external table layer needs to present the data to
the server. It is the responsibility of the access driver and the external table layer to do the necessary
transformations required on the data in the data file so that it matches the external table definition.
When the database server needs to access data in an external source, it calls the appropriate access driver to
get the data from an external source in a form that the database server expects.
It is important to remember that the description of the data in the data source is separate from the definition
of the external table. The source file can contain more or fewer fields than there are columns in the table.
Also, the data types for fields in the data source can be different from the columns in the table. The access
driver takes care of ensuring the data from the data source is processed so that it matches the definition of
the external table.

Introduction to Oracle9i: SQL 20-23

CREATE INDEX with CREATE TABLE Statement
CREATE TABLE NEW_EMP
(employee_id NUMBER(6)
PRIMARY KEY USING INDEX
(CREATE INDEX emp_id_idx ON
NEW_EMP(employee_id)),
first_name VARCHAR2(20),
last_name VARCHAR2(25));
Table created.
SELECT INDEX_NAME , TABLE_NAME
FROM USER_INDEXES
WHERE TABLE_NAME = 'NEW_EMP';
INDEX_NAME
-------------EMP_ID_IDX

20-24

TABLE_NAME
-----------------------------NEW_EMP

Copyright © Oracle Corporation, 2001. All rights reserved.

CREATE INDEX with CREATE TABLE Statement
In the example in the slide, the CREATE INDEX clause is used with the CREATE TABLE statement to
create a primary key index explicitly. This is an enhancement provided with Oracle 9i. You can now name
your indexes at the time of PRIMARY key creation, unlike before where the Oracle Server would create an
index, but you did not have any control over the name of the index. The following example illustrates this:
CREATE TABLE EMP_UNNAMED_INDEX
(employee_id NUMBER(6) PRIMARY KEY ,
first_name VARCHAR2(20),
last_name VARCHAR2(25));
Table created.
SELECT INDEX_NAME, TABLE_NAME
FROM USER_INDEXES
WHERE TABLE_NAME = 'EMP_UNNAMED_INDEX';

Observe that the Oracle Server gives a name to the Index that it creates for the PRIMARY KEY column.
But this name is cryptic and not easily understood. With Oracle9i, you can name your PRIMARY KEY
column indexes, as you create the table with the CREATE TABLE statement. However, prior to Oracle9i,
if you named your primary key constraint at the time of constraint creation, the index would also be created
with the same name as the constraint name.
Introduction to Oracle9i: SQL 20-24

Summary
In this lesson, you should have learned how to use the
following enhancements to DML and DDL statements:
• The INSERT…SELECT statement can be used to insert
rows into multiple tables as part of a single DML
statement.

•
•

External tables can be created.
Indexes can be named using the CREATE INDEX
statement along with the CREATE TABLE statement.

20-25

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
Oracle 9i introduces the following types of multitable INSERT statements.
•

Unconditional INSERT

•

Conditional ALL INSERT

•

Conditional FIRST INSERT

•

Pivoting INSERT

Use the external_table_clause to create an external table, which is a read-only table whose
metadata is stored in the database but whose data is stored outside the database. External tables let you
query data without first loading it into the database.
With Oracle9i, you can name your PRIMARY KEY column indexes as you create the table with the
CREATE TABLE statement.

Introduction to Oracle9i: SQL 20-25

Practice 20 Overview

This practice covers the following topics:
• Writing unconditional INSERT

•
•
•

20-26

Writing conditional ALL INSERT
Pivoting INSERT
Creating indexes along with the CREATE TABLE
command

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice 20 Overview
In this practice, you write multitable inserts and use the CREATE INDEX command at the time of table
creation, along with the CREATE TABLE command.

Introduction to Oracle9i: SQL 20-26

Practice 20
1. Run the cre_sal_history.sql script in the Labs folder to create the SAL_HISTORY table.
2. Display the structure of the SAL_HISTORY table.

3. Run the cre_mgr_history.sql script in the Labs folder to create the MGR_HISTORY table.
4. Display the structure of the MGR_HISTORY table.

5. Run the cre_special_sal.sql script in the Labs folder to create the SPECIAL_SAL table.
6. Display the structure of the SPECIAL_SAL table.

7. a. Write a query to do the following:
–

Retrieve the details of the employee ID, hire date, salary, and manager ID of those
employees whose employee ID is less than 125 from the EMPLOYEES table.

–

If the salary is more than $20,000, insert the details of employee ID and salary into the
SPECIAL_SAL table.

–

Insert the details of employee ID, hire date , salary into the SAL_HISTORY table.

–

Insert the details of the employee ID, manager ID, and salary into the MGR_HISTORY
table.

Introduction to Oracle9i: SQL 20-27

Practice 20 (continued)
b. Display the records from the SPECIAL_SAL table.

c. Display the records from the SAL_HISTORY table.

d. Display the records from the MGR_HISTORY table.

Introduction to Oracle9i: SQL 20-28

Practice 20 (continued)
8. a. Run the cre_sales_source_data.sql script in the Labs folder to create the
SALES_SOURCE_DATA table.
b. Run the ins_sales_source_data.sql script in the Labs folder to insert records into the
SALES_SOURCE_DATA table.
c. Display the structure of the SALES_SOURCE_DATA table.

d. Display the records from the SALES_SOURCE_DATA table.

e. Run the cre_sales_info.sql script in the Labs folder to create the SALES_INFO table.
f.

Display the structure of the SALES_INFO table.

Introduction to Oracle9i: SQL 20-29

Practice 20 (continued)
g.

Write a query to do the following:
Retrieve the details of employee ID, week ID, sales on Monday, sales on Tuesday, sales on Wednesday,
sales on Thursday, and sales on Friday from the SALES_SOURCE_DATA table.
Build a transformation such that each record retrieved from the SALES_SOURCE_DATA table is
converted into multiple records for the SALES_INFO table.
Hint: Use a pivoting INSERT statement.

h.

Display the records from the SALES_INFO table.

9. a. Create the DEPT_NAMED_INDEX table based on the following table instance chart. Name the index for
the PRIMARY KEY column as DEPT_PK_IDX.
COLUMN Name

Deptno

Dname

Primary Key

Yes

Datatype

Number

VARCHAR2

Length

4

30

b. Query the USER_INDEXES table to display the INDEX_NAME for the DEPT_NAMED_INDEX table.

Introduction to Oracle9i: SQL 20-30

Practice Solutions

Practice 1 Solutions
1. Initiate an iSQL*Plus session using the user ID and password provided by the instructor.
2. iSQL*Plus commands access the database.
False
3.

The following SELECT statement executes successfully:
True
SELECT last_name, job_id, salary AS Sal
FROM
employees;

4.

The following SELECT statement executes successfully:
True
SELECT *
FROM
job_grades;

5. There are four coding errors in this statement. Can you identify them?
SELECT
sal x 12
FROM

employee_id, last_name
ANNUAL SALARY
employees;

–

The EMPLOYEES table does not contain a column called sal. The column is called
SALARY.

–
–

The multiplication operator is *, not x, as shown in line 2.
The ANNUAL SALARY alias cannot include spaces. The alias should read
ANNUAL_SALARY or be enclosed in double quotation marks.

–

A comma is missing after the column, LAST_NAME.

6. Show the structure of the DEPARTMENTS table. Select all data from the DEPARTMENTS table.
DESCRIBE departments
SELECT *
FROM
departments;
7. Show the structure of the EMPLOYEES table. Create a query to display the last name, job code,
hire date, and employee number for each employee, with employee number appearing first. Save
your SQL statement to a file named lab1_7.sql.
DESCRIBE employees
SELECT employee_id, last_name, job_id, hire_date
FROM
employees;

Introduction to Oracle9i: SQL A-3

Practice 1 Solutions (continued)
8. Run your query in the file lab1_7.sql.
SELECT employee_id, last_name, job_id, hire_date
FROM
employees;
9.

Create a query to display unique job codes from the EMPLOYEES table.
SELECT DISTINCT job_id
FROM
employees;

If you have time, complete the following exercises:
10. Copy the statement from lab1_7.sql into the iSQL*Plus Edit window. Name the column
headings Emp #, Employee, Job, and Hire Date, respectively. Run your query again.
SELECT employee_id "Emp #", last_name "Employee",
job_id "Job", hire_date "Hire Date"
FROM
employees;
11. Display the last name concatenated with the job ID, separated by a comma and space, and name the
column Employee and Title.
SELECT last_name||', '||job_id "Employee and Title"
FROM
employees;
If you want an extra challenge, complete the following exercise:
12. Create a query to display all the data from the EMPLOYEES table. Separate each column by a
comma. Name the column THE_OUTPUT.
SELECT employee_id || ',' || first_name || ',' || last_name
|| ',' || email || ',' || phone_number || ','|| job_ id
|| ',' || manager_id || ',' || hire_date || ',' ||
salary || ',' || commission_pct || ',' || department _id
THE_OUTPUT
FROM
employees;

Introduction to Oracle9i: SQL A-4

Practice 2 Solutions
1. Create a query to display the last name and salary of employees earning more than $12,000.
Place your SQL statement in a text file named lab2_1.sql. Run your query.
SELECT
FROM
WHERE

last_name, salary
employees
salary > 12000;

2. Create a query to display the employee last name and department number for employee number
176.
SELECT
FROM
WHERE

last_name, department_id
employees
employee_id = 176;

3. Modify lab2_1.sql to display the last name and salary for all employees whose salary is not in
the range of $5,000 and $12,000. Place your SQL statement in a text file named lab2_3.sql.
SELECT
FROM
WHERE

last_name, salary
employees
salary NOT BETWEEN 5000 AND 12000;

4. Display the employee last name, job ID, and start date of employees hired between February 20,
1998, and May 1, 1998. Order the query in ascending order by start date.
SELECT
FROM
WHERE
ORDER BY

last_name, job_id, hire_date
employees
hire_date BETWEEN '20-Feb-1998' AND '01-May-1998'
hire_date;

Introduction to Oracle9i: SQL A-5

Practice 2 Solutions (continued)
5. Display the last name and department number of all employees in departments 20 and 50 in
alphabetical order by name.
SELECT
FROM
WHERE
ORDER BY

last_name, department_id
employees
department_id IN (20, 50)
last_name;

6. Modify lab2_3.sql to list the last name and salary of employees who earn between $5,000 and
$12,000, and are in department 20 or 50. Label the columns Employee and Monthly Salary,
respectively. Resave lab2_3.sql as lab2_6.sql. Run the statement in lab2_6.sql.
SELECT
FROM
WHERE
AND

last_name "Employee", salary "Monthly Salary"
employees
salary BETWEEN 5000 AND 12000
department_id IN (20, 50);

7. Display the last name and hire date of every employee who was hired in 1994.
SELECT
FROM
WHERE

last_name, hire_date
employees
hire_date LIKE '%94';

8. Display the last name and job title of all employees who do not have a manager.
SELECT
FROM
WHERE

last_name, job_id
employees
manager_id IS NULL;

9. Display the last name, salary, and commission for all employees who earn commissions. Sort
data in descending order of salary and commissions.
SELECT
FROM
WHERE
ORDER BY

last_name, salary, commission_pct
employees
commission_pct IS NOT NULL
salary DESC, commission_pct DESC;

Introduction to Oracle9i: SQL A-6

Practice 2 Solutions (continued)
If you have time, complete the following exercises.
10. Display the last names of all employees where the third letter of the name is an a.
SELECT
FROM
WHERE

last_name
employees
last_name LIKE '__a%';

11. Display the last name of all employees who have an a and an e in their last name.
SELECT
FROM
WHERE
AND

last_name
employees
last_name LIKE '%a%'
last_name LIKE '%e%';

If you want an extra challenge, complete the following exercises:
12. Display the last name, job, and salary for all employees whose job is sales representative or stock
clerk and whose salary is not equal to $2,500, $3,500, or $7,000.
SELECT
FROM
WHERE
AND

last_name, job_id, salary
employees
job_id IN ('SA_REP', 'ST_CLERK')
salary NOT IN (2500, 3500, 7000);

13. Modify lab2_6.sql to display the last name, salary, and commission for all employees whose
commission amount is 20%. Resave lab2_6.sql as lab2_13.sql. Rerun the statement in
lab2_13.sql.
.

SELECT
FROM
WHERE

last_name "Employee", salary "Monthly Salary",
commission_pct
employees
commission_pct = .20;

Introduction to Oracle9i: SQL A-7

Practice 3 Solutions
1. Write a query to display the current date. Label the column Date.
SELECT
FROM

sysdate "Date"
dual;

2. For each employee, display the employee number, last_name, salary, and salary increased by 15%
and expressed as a whole number. Label the column New Salary. Place your SQL statement in a
text file named lab3_2.sql.
SELECT
FROM

employee_id, last_name, salary,
ROUND(salary * 1.15, 0) "New Salary"
employees;

3. Run your query in the file lab3_2.sql.
SELECT
FROM

employee_id, last_name, salary,
ROUND(salary * 1.15, 0) "New Salary"
employees;

4. Modify your query lab3_2.sql to add a column that subtracts the old salary from
the new salary. Label the column Increase. Save the contents of the file as lab3_4.sql. Run
the revised query.
SELECT
employee_id, last_name, salary,
ROUND(salary * 1.15, 0) "New Salary",
ROUND(salary * 1.15, 0) - salary "Increase"
FROM
employees;
5. Write a query that displays the employee’s last names with the f irst letter capitalized and all other
letters lowercase and the length of the name for all employees whose name starts with J, A, or M.
Give each column an appropriate label. Sort the results by the employees’last names.
SELECT

INITCAP(last_name) "Name",
LENGTH(last_name) "Length"
FROM
employees
WHERE
last_name LIKE 'J%'
OR
last_name LIKE 'M%'
OR
last_name LIKE 'A%'
ORDER BY last_name;

Introduction to Oracle9i: SQL A-8

Practice 3 Solutions (continued)
6. For each employee, display the employee’s last name, and calculate the number of months between
today and the date the employee was hired. Label the column MONTHS_WORKED. Order your results
by the number of months employed. Round the number of months up to the closest whole number.
Note: Your results will differ.
SELECT

last_name, ROUND(MONTHS_BETWEEN
(SYSDATE, hire_date)) MONTHS_WORKED
FROM
employees
ORDER BY MONTHS_BETWEEN(SYSDATE, hire_date);
7.

Write a query that produces the following for each employee:
 earns  monthly but wants <3 times
salary>. Label the column Dream Salaries.
SELECT
last_name || ' earns '
|| TO_CHAR(salary, 'fm$99,999.00')
|| ' monthly but wants '
|| TO_CHAR(salary * 3, 'fm$99,999.00')
|| '.' "Dream Salaries"
FROM
employees;

If you have time, complete the following exercises:
8. Create a query to display the last name and salary for all employees. Format the salary to be 15
characters long, left-padded with $. Label the column SALARY.
SELECT
last_name,
LPAD(salary, 15, '$') SALARY
FROM
employees;
9. Display each employee’s last name, hire date, and salary review date, which is the first Monday after
six months of service. Label the column REVIEW. Format the dates to appear in the format similar to
“Monday, the Thirty-First of July, 2000.”
SELECT
last_name, hire_date,
TO_CHAR(NEXT_DAY(ADD_MONTHS(hire_date, 6),'MONDAY'),
'fmDay, "the" Ddspth "of" Month, YYYY') REVIEW
FROM
employees;
10. Display the last name, hire date, and day of the week on which the employee started. Label
the column DAY. Order the results by the day of the week starting with Monday.
SELECT

last_name, hire_date,
TO_CHAR(hire_date, 'DAY') DAY
FROM
employees
ORDER BY TO_CHAR(hire_date - 1, 'd');

Introduction to Oracle9i: SQL A-9

Practice 3 Solutions (continued)
If you want an extra challenge, complete the following exercises:
11. Create a query that displays the employees’last names and commission amounts. If an employee
does not earn commission, put “No Commission.” Label the column COMM.
SELECT
FROM

last_name,
NVL(TO_CHAR(commission_pct), 'No Commission') COM M
employees;

12. Create a query that displays the employees’last names and indicates the amounts of their annual
salaries with asterisks. Each asterisk signifies a thousand doll ars. Sort the data in descending order
of salary. Label the column EMPLOYEES_AND_THEIR_SALARIES.
SELECT

rpad(last_name, 8)||' '|| rpad(' ', salary/1000+1, '*')
EMPLOYEES_AND_THEIR_SALARIES
FROM
employees
ORDER BY salary DESC;
13. Using the DECODE function, write a query that displays the grade of all employees based on the
value of the column JOB_ID, as per the following data:
JOB

GRADE

AD_PRES

A

ST_MAN

B

IT_PROG

C

SA_REP

D

ST_CLERK

E

None of the above

0

SELECT job_id, decode (job_id,
'ST_CLERK',
'SA_REP',
'IT_PROG',
'ST_MAN',
'AD_PRES',

'E',
'D',
'C',
'B',
'A',
'0')GRADE

FROM employees;

Introduction to Oracle9i: SQL A-10

Practice 3 Solutions (continued)
14. Rewrite the statement in the preceding question using the CASE syntax.
SELECT job_id, CASE job_id
WHEN 'ST_CLERK' THEN
WHEN 'SA_REP'
THEN
WHEN 'IT_PROG' THEN
WHEN 'ST_MAN'
THEN
WHEN 'AD_PRES' THEN
ELSE '0' END GRADE
FROM employees;

'E'
'D'
'C'
'B'
'A'

Introduction to Oracle9i: SQL A-11

Practice 4 Solutions
1. Write a query to display the last name, department number, and department name for all
employees.
SELECT e.last_name, e.department_id, d.department_name
FROM employees e, departments d
WHERE e.department_id = d.department_id;
2. Create a unique listing of all jobs that are in department 30. Include the location of department 90
in the output.
SELECT DISTINCT job_id, location_id
FROM employees, departments
WHERE employees.department_id = departments.department_id
AND employees.department_id = 80;
3. Write a query to display the employee last name, department name, location ID, and city of all
employees who earn a commission.
SELECT e.last_name, d.department_name, d.location_id, l.c ity
FROM employees e, departments d, locations l
WHERE e.department_id = d.department_id
AND
d.location_id = l.location_id
AND e.commission_pct IS NOT NULL;
4. Display the employee last name and department name for all employees who have an a (lowercase)
in their last names. Place your SQL statement in a text file named lab4_4.sql.
SELECT last_name, department_name
FROM employees, departments
WHERE employees.department_id = departments.department_id
AND last_name LIKE '%a%';

Introduction to Oracle9i: SQL A-12

Practice 4 Solutions (continued)
5. Write a query to display the last name, job, department number, and department name for all
employees who work in Toronto.
SELECT e.last_name, e.job_id, e.department_id,
d.department_name
FROM employees e JOIN departments d
ON (e.department_id = d.department_id)
JOIN locations l
ON (d.location_id = l.location_id)
WHERE LOWER(l.city) = 'toronto';
6. Display the employee last name and employee number along with their manager’s last name and
manager number. Label the columns Employee, Emp#, Manager, and Mgr#, respectively.
Place your SQL statement in a text file named lab4_6.sql.
SELECT w.last_name "Employee", w.employee_id "EMP#",
m.last_name "Manager", m.employee_id "Mgr#"
FROM employees w join employees m
ON (w.manager_id = m.employee_id);

Introduction to Oracle9i: SQL A-13

Practice 4 Solutions (continued)
7. Modify lab4_6.sql to display all employees including King, who has no manager.
Place your SQL statement in a text file named lab4_7.sql. Run the query in lab4_7.sql
SELECT w.last_name "Employee", w.employee_id "EMP#",
m.last_name "Manager", m.employee_id "Mgr#"
FROM employees w
LEFT OUTER JOIN employees m
ON (w.manager_id = m.employee_id);
If you have time, complete the following exercises.
8. Create a query that displays employee last names, department numbers, and all the
employees who work in the same department as a given employee. Give each column an appropriate
label.
SELECT e.department_id department, e.last_name employee,
c.last_name colleague
FROM
employees e JOIN employees c
ON
(e.department_id = c.department_id)
WHERE
e.employee_id <> c.employee_id
ORDER BY e.department_id, e.last_name, c.last_name;
9. Show the structure of the JOB_GRADES table. Create a query that displays the name, job,
department name, salary, and grade for all employees.
DESC JOB_GRADES
SELECT e.last_name, e.job_id, d.department_name,
e.salary, j.grade_level
FROM
employees e, departments d, job_grades j
WHERE e.department_id = d.department_id
AND
e.salary BETWEEN j.lowest_sal AND j.highest_sal;
-- OR
SELECT e.last_name, e.job_id, d.department_name,
e.salary, j.grade_level
FROM
employees e JOIN departments d
ON
(e.department_id = d.department_id)
JOIN
job_grades j
ON
(e.salary BETWEEN j.lowest_sal AND j.highest_sal);

Introduction to Oracle9i: SQL A-14

Practice 4 Solutions (continued)
If you want an extra challenge, complete the following exercises:
10. Create a query to display the name and hire date of any employee hired after employee Davies.
SELECT
FROM
WHERE
AND
-- OR
SELECT
FROM
ON
WHERE

e.last_name, e.hire_date
employees e, employees davies
davies.last_name = 'Davies'
davies.hire_date < e.hire_date
e.last_name, e.hire_date
employees e JOIN employees davies
(davies.last_name = 'Davies')
davies.hire_date < e.hire_date;

11. Display the names and hire dates for all employees who were hired before their managers, along with
their manager’s names and hire dates. Label the columns Employee, Emp
Hired, Manager, and Mgr Hired, respectively.
SELECT w.last_name, w.hire_date, m.last_name, m.hire_date
FROM
employees w, employees m
WHERE w.manager_id = m.employee_id
AND
w.hire_date < m.hire_date;
-- OR
SELECT w.last_name, w.hire_date, m.last_name, m.hire_date
FROM
employees w JOIN employees m
ON
(w.manager_id = m.employee_id)
WHERE
w.hire_date < m.hire_date;

Introduction to Oracle9i: SQL A-15

Practice 5 Solutions
Determine the validity of the following three statements. Circle either True or False.
1. Group functions work across many rows to produce one result.
True
2. Group functions include nulls in calculations.
False. Group functions ignore null values. If you want to include null values, use the NVL
function.
3. The WHERE clause restricts rows prior to inclusion in a group calculation.
True
4. Display the highest, lowest, sum, and average salary of all employees. Label the columns
Maximum, Minimum, Sum, and Average, respectively. Round your results to the nearest whole
number. Place your SQL statement in a text file named lab5_6.sql.
SELECT

FROM

ROUND(MAX(salary),0)
ROUND(MIN(salary),0)
ROUND(SUM(salary),0)
ROUND(AVG(salary),0)
employees;

"Maximum",
"Minimum",
"Sum",
"Average"

5. Modify the query in lab5_4.sql to display the minimum, maximum, sum, and average salary for
each job type. Resave lab5_4.sql to lab5_5.sql. Run the statement in lab5_5.sql.
SELECT

job_id, ROUND(MAX(salary),0)
ROUND(MIN(salary),0)
ROUND(SUM(salary),0)
ROUND(AVG(salary),0)
FROM
employees
GROUP BY job_id;

"Maximum",
"Minimum",
"Sum",
"Average"

Introduction to Oracle9i: SQL A-16

Practice 5 Solutions (continued)
6. Write a query to display the number of people with the same job.
SELECT
job_id, COUNT(*)
FROM
employees
GROUP BY job_id;
7. Determine the number of managers without listing them. Label the column Number of
Managers. Hint: Use the MANAGER_ID column to determine the number of managers.
SELECT
FROM

COUNT(DISTINCT manager_id) "Number of Managers"
employees;

8. Write a query that displays the difference between the highest a nd lowest salaries. Label the column
DIFFERENCE.
SELECT
FROM

MAX(salary) - MIN(salary) DIFFERENCE
employees;

If you have time, complete the following exercises.
9. Display the manager number and the salary of the lowest paid employee for that manager.
Exclude anyone whose manager is not known. Exclude any groups where the minimum
salary is less than $6,000. Sort the output in descending order of salary.
SELECT
FROM
WHERE
GROUP BY
HAVING
ORDER BY

manager_id, MIN(salary)
employees
manager_id IS NOT NULL
manager_id
MIN(salary) > 6000
MIN(salary) DESC;

10. Write a query to display each department’s name, location, number of employees, and the average
salary for all employees in that department. Label the columns Name, Location, Number of
People, and Salary, respectively. Round the average salary to two decimal places.
SELECT

d.department_name "Name", d.location_id "Location ",
COUNT(*) "Number of People",
ROUND(AVG(salary),2) "Salary"
FROM
employees e, departments d
WHERE
e.department_id = d.department_id
GROUP BY d.department_name, d.location_id;

Introduction to Oracle9i: SQL A-17

Practice 5 Solutions (continued)
If you want an extra challenge, complete the following exercises:
11. Create a query that will display the total number of employees and, of that total, the number of
employees hired in 1995, 1996, 1997, and 1998. Create appropriate column headings.
SELECT

FROM

COUNT(*) total,
SUM(DECODE(TO_CHAR(hire_date,
SUM(DECODE(TO_CHAR(hire_date,
SUM(DECODE(TO_CHAR(hire_date,
SUM(DECODE(TO_CHAR(hire_date,
employees;

'YYYY'),1995,1,0))"1 995",
'YYYY'),1996,1,0))"1 996",
'YYYY'),1997,1,0))"1 997",
'YYYY'),1998,1,0))"1 998"

12. Create a matrix query to display the job, the salary for that job based on department number, and the
total salary for that job, for departments 20, 50, 80, and 90, giving each column an appropriate
heading.

SELECT

job_id "Job",
SUM(DECODE(department_id
SUM(DECODE(department_id
SUM(DECODE(department_id
SUM(DECODE(department_id
SUM(salary) "Total"
FROM
employees
GROUP BY job_id;

,
,
,
,

20,
50,
80,
90,

salary))
salary))
salary))
salary))

Introduction to Oracle9i: SQL A-18

"Dept
"Dept
"Dept
"Dept

20" ,
50" ,
80" ,
90" ,

Practice 6 Solutions
1. Write a query to display the last name and hire date of any employee in the same
department as Zlotkey. Exclude Zlotkey.
SELECT last_name, hire_date
FROM
employees
WHERE department_id = (SELECT department_id
FROM
employees
WHERE last_name = 'Zlotkey')
AND
last_nae <> 'Zlotkey';
2. Create a query to display the employee numbers and last names of all employees who earn more than
the average salary. Sort the results in descending order of salary.
SELECT employee_id, last_name
FROM
employees
WHERE salary > (SELECT AVG(salary)
FROM
employees);

3.

Write a query that displays the employee numbers and last names of all employees who work in a
department with any employee whose last name contains a u. Place your SQL statement in a text
file named lab6_3.sql. Run your query.
SELECT employee_id, last_name
FROM
employees
WHERE department_id IN (SELECT department_id
FROM
employees
WHERE last_name like '%u%');

4. Display the last name, department number, and job ID of all employees whose department location ID
is 1700.
SELECT last_name, department_id, job_id
FROM
employees
WHERE department_id IN (SELECT department_id
FROM
departments
WHERE location_id = 1700);

Introduction to Oracle9i: SQL A-19

Practice 6 Solutions (continued)
5. Display the last name and salary of every employee who reports to King.
SELECT last_name, salary
FROM
employees
WHERE manager_id = (SELECT employee_id
FROM
employees
WHERE last_name = 'King');
6. Display the department number, last name, and job ID for every employee in the Executive
department.
SELECT department_id, last_name, job_id
FROM
employees
WHERE department_id IN (SELECT department_id
FROM
departments
WHERE department_name = 'Executive' );
If you have time, complete the following exercises:
7. Modify the query in lab6_3.sql to display the employee numbers, last names, and salaries of all
employees who earn more than the average salary and who work in a department with any employee
with a u in their name. Resave lab6_3.sql to lab6_7.sql. Run the statement in
lab6_7.sql.
SELECT employee_id, last_name, salary
FROM
employees
WHERE department_id IN (SELECT department_id
FROM
employees
WHERE last_name like '%u%')
AND
salary > (SELECT AVG(salary)
FROM
employees);

Introduction to Oracle9i: SQL A-20

Practice 7 Solutions
Determine whether the following statements are true or false:
1. The following statement is correct:
DEFINE & p_val = 100
False
The correct use of DEFINE is DEFINE p_val=100. The & is used within the SQL code.
2. The DEFINE command is a SQL command.
False
The DEFINE command is an iSQL*Plus command.
3. Write a script file to display the employee last name, job, and hire date for all employees who
started between a given range. Concatenate the name and job together, separated by a space
and comma, and label the column Employees. Use the DEFINE command to provide the two
ranges. Use the format MM/DD/YYYY. Save the script file as lab7_3.sql.

SET ECHO OFF
SET VERIFY OFF
DEFINE low_date = 01/01/1998
DEFINE high_date = 01/01/1999
SELECT
FROM
WHERE

last_name ||', '|| job_id EMPLOYEES, hire_date
employees
hire_date BETWEEN TO_DATE('&low_date', 'MM/DD/YYYY')
AND TO_DATE('&high_date', 'MM/DD/YY YY')

/
UNDEFINE low_date
UNDEFINE high_date
SET VERIFY ON
SET ECHO ON

Introduction to Oracle9i: SQL A-21

Practice 7 Solutions (continued)
4. Write a script to display the employee last name, job, and department name for a given location. The
search condition should allow for case-insensitive searches of the department location. Save the
script file as lab7_4.sql.
SET ECHO OFF
SET VERIFY OFF
COLUMN last_name HEADING "EMPLOYEE NAME"
COLUMN department_name HEADING "DEPARTMENT NAME”
SELECT e.last_name, e.job_id, d.department_name
FROM
employees e, departments d, locations l
WHERE
e.department_id = d.department_id
AND
l.location_id = d.location_id
AND
l.city = INITCAP('&p_location')
/
COLUMN last_name CLEAR
COLUMN department_name CLEAR
SET VERIFY ON
SET ECHO ON

Introduction to Oracle9i: SQL A-22

Practice 7 Solutions (continued)
5. Modify the code in lab7_4.sql to create a report containing the department name, employee last
name, hire date, salary, and each employee’s annual salary for all employees in a given location.
Label the columns DEPARTMENT NAME, EMPLOYEE NAME, START DATE, SALARY, and
ANNUAL SALARY, placing the labels on multiple lines. Resave the script as lab7_5.sql and
execute the commands in the script.
SET ECHO OFF
SET FEEDBACK OFF
SET VERIFY OFF
BREAK ON department_name
COLUMN department_name HEADING "DEPARTMENT|NAME"
COLUMN last_name HEADING "EMPLOYEE|NAME"
COLUMN hire_date HEADING "START|DATE"
COLUMN salary HEADING "SALARY" FORMAT $99,990.00
COLUMN asal HEADING "ANNUAL|SALARY" FORMAT $99,990.00
SELECT d.department_name, e.last_name, e.hire_date,
e.salary, e.salary*12 asal
FROM
departments d, employees e, locations l
WHERE e.department_id = d.department_id
AND
d.location_id
= l.location_id
AND
l.city
= '&p_location'
ORDER BY d.department_name
/
COLUMN department_name CLEAR
COLUMN last_name CLEAR
COLUMN hire_date CLEAR
COLUMN salary CLEAR
COLUMN asal CLEAR
CLEAR BREAK
SET VERIFY ON
SET FEEDBACK ON
SET ECHO ON

Introduction to Oracle9i: SQL A-23

Practice 8 Solutions
Insert data into the MY_EMPLOYEE table.
1. Run the statement in the lab8_1.sql script to build the MY_EMPLOYEE table that will be used for
the lab.
CREATE TABLE my_employee
(id NUMBER(4) CONSTRAINT my_employee_id_ nn NOT NULL,
last_name VARCHAR2(25),
first_name VARCHAR2(25),
userid VARCHAR2(8),
salary NUMBER(9,2));

2. Describe the structure of the MY_EMPLOYEE table to identify the column names.
DESCRIBE my_employee
3. Add the first row of data to the MY_EMPLOYEE table from the following sample data. Do not list the
columns in the INSERT clause.

ID

LAST_NAME

FIRST_NAME

USERID

SALARY

1

Patel

Ralph

rpatel

895

2

Dancs

Betty

bdancs

860

3

Biri

Ben

bbiri

1100

4

Newman

Chad

cnewman

750

5

Ropeburn

Audrey

aropebur

1550

INSERT INTO my_employee
VALUES (1, 'Patel', 'Ralph', 'rpatel', 895);
4. Populate the MY_EMPLOYEE table with the second row of sample data from the preceding list. This
time, list the columns explicitly in the INSERT clause.
INSERT INTO my_employee (id, last_name, first_name,
userid, salary)
VALUES (2, 'Dancs', 'Betty', 'bdancs', 860);
5. Confirm your addition to the table.
SELECT
FROM

*
my_employee;

Introduction to Oracle9i: SQL A-24

Practice 8 Solutions (continued)
6. Write an insert statement in a text file named loademp.sql to load rows into the
MY_EMPLOYEE table. Concatenate the first letter of the first name and the first seven characters of
the last name to produce the userid.
SET ECHO OFF
SET VERIFY OFF
INSERT INTO my_employee
VALUES (&p_id, '&p_last_name', '&p_first_name',
lower(substr('&p_first_name', 1, 1) ||
substr('&p_last_name', 1, 7)), &p_salary);
SET VERIFY ON
SET ECHO ON
7. Populate the table with the next two rows of sample data by running the insert statement in the
script that you created.
SET ECHO OFF
SET VERIFY OFF
INSERT INTO my_employee
VALUES (&p_id, '&p_last_name', '&p_first_name',
lower(substr('&p_first_name', 1, 1) ||
substr('&p_last_name', 1, 7)), &p_salary);
SET VERIFY ON
SET ECHO ON
8. Confirm your additions to the table.
SELECT
*
FROM my_employee;
9. Make the data additions permanent.
COMMIT;

Introduction to Oracle9i: SQL A-25

Practice 8 Solutions (continued)
Update and delete data in the MY_EMPLOYEE table.
10. Change the last name of employee 3 to Drexler.
UPDATE
SET
WHERE

my_employee
last_name = 'Drexler'
id = 3;

11. Change the salary to 1000 for all employees with a salary less than 900.
UPDATE
SET
WHERE

my_employee
salary = 1000
salary < 900;

12. Verify your changes to the table.
SELECT
FROM

last_name, salary
my_employee;

13. Delete Betty Dancs from the MY_EMPLOYEE table.
DELETE
FROM my_employee
WHERE last_name = 'Dancs';
14. Confirm your changes to the table.
SELECT
FROM

*
my_employee;

15. Commit all pending changes.
COMMIT;
Control data transaction to the MY_EMPLOYEE table.
16. Populate the table with the last row of sample data by modifying the statements in the script that you
created in step 6. Run the statements in the script.
SET ECHO OFF
SET VERIFY OFF
INSERT INTO my_employee
VALUES (&p_id, '&p_last_name', '&p_first_name',
lower(substr('&p_first_name', 1, 1) ||
substr('&p_last_name', 1, 7)), &p_salary);
SET VERIFY ON
SET ECHO ON

Introduction to Oracle9i: SQL A-26

Practice 8 Solutions (continued)
17. Confirm your addition to the table.
SELECT
*
FROM my_employee;
18. Mark an intermediate point in the processing of the transaction.
SAVEPOINT step_18;
19. Empty the entire table.
DELETE
FROM my_employee;
20. Confirm that the table is empty.
SELECT *
FROM
my_employee;
21. Discard the most recent DELETE operation without discarding the earlier INSERT operation.
ROLLBACK TO step_18;
22. Confirm that the new row is still intact.
SELECT *
FROM
my_employee;
23. Make the data addition permanent.
COMMIT;

Introduction to Oracle9i: SQL A-27

Practice 9 Solutions
1. Create the DEPT table based on the following table instance chart. Place the syntax in a script called
lab9_1.sql, then execute the statement in the script to create the table. Confirm that the table is
created.

ID

NAME

Data type

Number

VARCHAR2

Length

7

25

Column Name
Key Type
Nulls/Unique
FK Table
FK Column

CREATE TABLE dept
(id NUMBER(7),
name VARCHAR2(25));
DESCRIBE dept
2.

Populate the DEPT table with data from the DEPARTMENTS table. Include only columns that
you need.
INSERT INTO dept
SELECT department_id, department_name
FROM
departments;

3. Create the EMP table based on the following table instance chart. Place the syntax in a script called
lab9_3.sql, and then execute the statement in the script to create the table. Confirm that the table is
created.

ID

LAST_NAME

FIRST_NAME

DEPT_ID

Data type

Number

VARCHAR2

VARCHAR2

Number

Length

7

25

25

7

Column Name
Key Type
Nulls/Unique
FK Table
FK Column

Introduction to Oracle9i: SQL A-28

Practice 9 Solutions (continued)
CREATE TABLE
(id
last_name
first_name
dept_id

emp
NUMBER(7),
VARCHAR2(25),
VARCHAR2(25),
NUMBER(7));

DESCRIBE emp
4. Modify the EMP table to allow for longer employee last names. Confirm your modification.
ALTER TABLE emp
MODIFY (last_name

VARCHAR2(50));

DESCRIBE emp
5. Confirm that both the DEPT and EMP tables are stored in the data dictionary. (Hint:
USER_TABLES)
SELECT
FROM
WHERE

table_name
user_tables
table_name IN ('DEPT', 'EMP');

6. Create the EMPLOYEES2 table based on the structure of the EMPLOYEES table. Include only the
EMPLOYEE_ID, FIRST_NAME, LAST_NAME, SALARY, and DEPARTMENT_ID columns. Name
the columns in your new table ID, FIRST_NAME, LAST_NAME, SALARY , and DEPT_ID,
respectively.
CREATE TABLE employees2 AS
SELECT employee_id id, first_name, last_name, salary,
FROM

department_id dept_id
employees;

7. Drop the EMP table.
DROP TABLE emp;
8. Rename the EMPLOYEES2 table to EMP.
RENAME employees2 TO emp;

Introduction to Oracle9i: SQL A-29

Practice 9 Solutions (continued)
9. Add a comment to the DEPT and EMP table definitions describing the tables. Confirm your additions
in the data dictionary.
COMMENT
COMMENT
SELECT
FROM
WHERE
OR

ON TABLE emp IS 'Employee Information';
ON TABLE dept IS 'Department Information';
*
user_tab_comments
table_name = 'DEPT'
table_name = 'EMP';

10. Drop the FIRST_NAME column from the EMP table. Confirm your modification by checking the
description of the table.
ALTER TABLE emp
DROP COLUMN FIRST_NAME;
DESCRIBE emp
11. In the EMP table, mark the DEPT_ID column in the EMP table as UNUSED. Confirm your
modification by checking the description of the table.
ALTER TABLE
emp
SET
UNUSED (dept_id);
DESCRIBE emp
12. Drop all the UNUSED columns from the EMP table. Confirm your modification by checking the
description of the table.
ALTER TABLE emp
DROP UNUSED COLUMNS;
DESCRIBE emp

Introduction to Oracle9i: SQL A-30

Practice 10 Solutions
1. Add a table-level PRIMARY KEY constraint to the EMP table on the ID column. The constraint
should be named at creation. Name the constraint my_emp_id_pk
ALTER TABLE
emp
ADD CONSTRAINT my_emp_id_pk PRIMARY KEY (id);
2. Create a PRIMARY KEY constraint to the DEPT table using the ID column. The constraint should
be named at creation. Name the constraint my_deptid_pk.
ALTER TABLE
dept
ADD CONSTRAINT my_deptid_pk PRIMARY KEY(id);
3. Add a column DEPT_ID to the EMP table. Add a foreign key reference on the EMP table that
ensures that the employee is not assigned to a nonexistent department. Name the constraint
my_emp_dept_id_fk.
ALTER TABLE emp
ADD (dept_id NUMBER(7));
ALTER TABLE emp
ADD CONSTRAINT my_emp_dept_id_ fk
FOREIGN KEY (dept_id) REFERENCES dept(id);
4. Confirm that the constraints were added by querying the USER_CONSTRAINTS view. Note the
types and names of the constraints. Save your statement text in a file called lab10_4.sql.
SELECT
FROM
WHERE

constraint_name, constraint_type
user_constraints
table_name IN ('EMP', 'DEPT');

5. Display the object names and types from the USER_OBJECTS data dictionary view for the EMP
and DEPT tables. Notice that the new tables and a new index were created.
SELECT
FROM
WHERE
OR

object_name, object_type
user_objects
object_name LIKE 'EMP%'
object_name LIKE 'DEPT%';

If you have time, complete the following exercise:
6. Modify the EMP table. Add a COMMISSION column of NUMBER data type, precision 2, scale 2.
Add a constraint to the commission column that ensures that a commission value is greater than
zero.
ALTER TABLE EMP
ADD commission NUMBER(2,2)
CONSTRAINT my_emp_comm_ck CHECK (commission >= 0;

Introduction to Oracle9i: SQL A-31

Practice 11 Solutions
1. Create a view called EMPLOYEES_VU based on the employee numbers, employee names, and
department numbers from the EMPLOYEES table. Change the heading for the employee name to
EMPLOYEE.
CREATE OR REPLACE VIEW employees_vu AS
SELECT employee_id, last_name employee, department_id
FROM employees;
2. Display the contents of the EMPLOYEES_VU view.
SELECT
FROM

*
employees_vu;

3. Select the view name and text from the USER_VIEWS data dictionary view.
Note: Another view already exists. The EMP_DETAILS_VIEW was created as part of your schema.
Note: To see more contents of a LONG column, use the iSQL*Plus command SET LONG n, where
n is the value of the number of characters of the LONG column that you want to see.
SET LONG 600
SELECT
view_name, text
FROM
user_views;
4. Using your EMPLOYEES_VU view, enter a query to display all employee names and department
numbers.
SELECT
employee, department_id
FROM
employees_vu;
5. Create a view named DEPT50 that contains the employee numbers, employee last names, and
department numbers for all employees in department 50. Label the view columns
EMPNO, EMPLOYEE, and DEPTNO. Do not allow an employee to be reassigned to another
department through the view.
CREATE VIEW dept50 AS
SELECT
employee_id empno, last_name employee,
department_id deptno
FROM
employees
WHERE
department_id = 50
WITH CHECK OPTION CONSTRAINT emp_dept_50;

Introduction to Oracle9i: SQL A-32

Practice 11 Solutions (continued)
6. Display the structure and contents of the DEPT50 view.
DESCRIBE dept50
SELECT
*
FROM
dept50;
7. Attempt to reassign Matos to department 80.
UPDATE
SET
WHERE

dept50
deptno = 80
employee = 'Matos';

If you have time, complete the following exercise:
8. Create a view called SALARY_VU based on the employee last names, department names, salaries,
and salary grades for all employees. Use the EMPLOYEES, DEPARTMENTS, and JOB_GRADES
tables. Label the columns Employee, Department, Salary, and Grade, respectively.
CREATE OR REPLACE VIEW salary_vu
AS
SELECT e.last_name "Employee",
d.department_name "Department",
e.salary "Salary",
j.grade_level "Grades"
FROM
employees e,
departments d,
job_grades j
WHERE e.department_id = d.department_id
AND
e.salary BETWEEN j.lowest_sal and j.highest_sal;

Introduction to Oracle9i: SQL A-33

Practice 12 Solutions
1. Create a sequence to be used with the primary key column of the DEPT table. The sequence should
start at 200 and have a maximum value of 1000. Have your sequence increment by ten numbers.
Name the sequence DEPT_ID_SEQ.
CREATE SEQUENCE dept_id_seq
START WITH 200
INCREMENT BY 10
MAXVALUE 1000;
2. Write a query in a script to display the following information about your sequences: sequence name,
maximum value, increment size, and last number. Name the script lab12_2.sql. Run the
statement in your script.
SELECT
FROM

sequence_name, max_value, increment_by, last_number
user_sequences;

3. Write a script to insert two rows into the DEPT table. Name your script
lab12_3.sql.
Be sure to use the sequence that you created for the ID column. Add two departments named
Education and Administration. Confirm your additions. Run the commands in your script.
INSERT INTO dept
VALUES (dept_id_seq.nextval, 'Education');
INSERT INTO dept
VALUES (dept_id_seq.nextval, 'Administration');
4. Create a nonunique index on the foreign key column (DEPT_ID) in the EMP table.
CREATE INDEX emp_dept_id_idx ON emp (dept_id);
5. Display the indexes and uniqueness that exist in the data dictio nary for the EMP table. Save the
statement into a script named lab12_5.sql.
SELECT
FROM
WHERE

index_name, table_name, uniqueness
user_indexes
table_name = 'EMP';

Introduction to Oracle9i: SQL A-34

Practice 13 Solutions
1. What privilege should a user be given to log on to the Oracle Server? Is this a system or an object
privilege?
The CREATE SESSION system privilege
2. What privilege should a user be given to create tables?
The CREATE TABLE privilege
3. If you create a table, who can pass along privileges to other users on your table?
You can, or anyone you have given those privileges to by using the WITH GRANT
OPTION.
4. You are the DBA. You are creating many users who require the same system privileges.
What should you use to make your job easier?
Create a role containing the system privileges and grant the role to the users
5. What command do you use to change your password?
The ALTER USER statement
6. Grant another user access to your DEPARTMENTS table. Have the user grant you query access to his
or her DEPARTMENTS table.
Team 2 executes the GRANT statement.
GRANT select
ON
departments
TO
;
Team 1 executes the GRANT statement.
GRANT select
ON
departments
TO
;
WHERE user1 is the name of team 1 and user2 is the name of team 2.

7.

Query all the rows in your DEPARTMENTS table.
SELECT
FROM

*
departments;

Introduction to Oracle9i: SQL A-35

Practice 13 Solutions (continued)
8. Add a new row to your DEPARTMENTS table. Team 1 should add Education as department
number 500. Team 2 should add Human Resources department number 510. Query the other team’s
table.
Team 1 executes this INSERT statement.
INSERT INTO departments(department_id, department_name)
VALUES (200, 'Education');
COMMIT;
Team 2 executes this INSERT statement.
INSERT INTO departments(department_id, department_name)
VALUES (210, 'Administration');
COMMIT;
9. Create a synonym for the other team’s DEPARTMENTS table.
Team 1 creates a synonym named team2.
CREATE SYNONYM
team2
FOR .DEPARTMENTS;
Team 2 creates a synonym named team1.
CREATE SYNONYM
team1
FOR . DEPARTMENTS;
10. Query all the rows in the other team’s DEPARTMENTS table by using your synonym.
Team 1 executes this SELECT statement.
SELECT

*

FROM

team2;

Team 2 executes this SELECT statement.
SELECT

*

FROM

team1;

Introduction to Oracle9i: SQL A-36

Practice 13 Solutions (continued)
11. Query the USER_TABLES data dictionary to see information about the tables that you own.
SELECT
FROM

table_name
user_tables;

12. Query the ALL_TABLES data dictionary view to see information about all the tables that you
can access. Exclude tables that you own.
SELECT
FROM
WHERE

table_name, owner
all_tables
owner <> ;

13. Revoke the SELECT privilege from the other team.
Team 1 revokes the privilege.
REVOKE select
ON
departments
FROM
user2;
Team 2 revokes the privilege.
REVOKE select
ON
departments
FROM
user1;

Introduction to Oracle9i: SQL A-37

Practice 14 Solutions
1. Create the tables based on the following table instance charts. Choose the appropriate data types and
be sure to add integrity constraints.
a. Table name: MEMBER
Column_
Name

MEMBER_
ID

Key
Type
Null/
Unique
Default
Value

PK

Data
Type
Length

NN,U

LAST_
NAME

FIRST_NAM
E

ADDRESS

CITY

PHONE

JOIN
_
DATE

NN

NN

NUMBER

VARCHAR2

VARCHAR2

VARCHAR2

VARCHAR2

VARCHAR2

System
Date
DATE

10

25

25

100

30

15

CREATE TABLE member
(member_id

NUMBER(10)
CONSTRAINT member_member_id_pk PRIMARY KEY,
last_name
VARCHAR2(25)
CONSTRAINT member_last_name_nn NOT NULL,
first_name
VARCHAR2(25),
address
VARCHAR2(100),
city VARCHAR2(30),
phone
VARCHAR2(15),
join_date
DATE DEFAULT SYSDATE
CONSTRAINT member_join_date_nn NOT NULL);

Introduction to Oracle9i: SQL A-38

Practice 14 Solutions (continued)
b. Table name: TITLE
Column_
Name

TITLE_ID

Key
Type
Null/
Unique
Check

PK

Data Type

NUMBER

VARCHAR2

VARCHAR2

Length

10

60

400

NN,U

TITLE

DESCRIPTION

NN

NN

RATING

CATEGORY

G, PG, R,
NC17, NR

VARCHAR2

DRAMA,
COMEDY,
ACTION,
CHILD,
SCIFI,
DOCUMENTARY
VARCHAR2

4

20

CREATE TABLE title
(title_id NUMBER(10)
CONSTRAINT title_title_id_pk PRIMARY KEY,
title
VARCHAR2(60)
CONSTRAINT title_title_nn NOT NULL,
description
VARCHAR2(400)
CONSTRAINT title_description_nn NOT NULL,
rating
VARCHAR2(4)
CONSTRAINT title_rating_ck CHECK
(rating IN ('G', 'PG', 'R', 'NC17', 'NR')),
category VARCHAR2(20),
CONSTRAINT title_category_ck CHECK
(category IN ('DRAMA', 'COMEDY', 'ACTION',
'CHILD', 'SCIFI', 'DOCUMENTARY')),
release_date DATE);

Introduction to Oracle9i: SQL A-39

RELEASE_
DATE

DATE

Practice 14 Solutions (continued)
c. Table name: TITLE_COPY

Column
Name
Key
Type
Null/
Unique
Check

FK Ref
Table
FK Ref
Column
Data
Type
Length

COPY_ID

TITLE_ID

PK

PK,FK

NN,U

NN,U

STATUS

NN
AVAILABLE,
DESTROYED,
RENTED,
RESERVED

TITLE
TITLE_ID
NUMBER

NUMBER

VARCHAR2

10

10

15

CREATE TABLE title_copy
(copy_id
NUMBER(10),
title_id
NUMBER(10)
CONSTRAINT title_copy_title_if_ fk REFERENCES title(title_id),
status
VARCHAR2(15)
CONSTRAINT title_copy_status_nn NOT NULL
CONSTRAINT title_copy_status_ck CHECK (status IN
('AVAILABLE', 'DESTROYED','RENTED', 'RESERVED')),
CONSTRAINT title_copy_copy_id_title_id_ pk
PRIMARY KEY (copy_id, title_id));

Introduction to Oracle9i: SQL A-40

Practice 14 Solutions (continued)
d. Table name: RENTAL

Column
Name
Key
Type
Default
Value
FK Ref
Table
FK Ref
Column
Data
Type
Length

BOOK_
DATE
PK

MEMBER_
ID
PK,FK1

COPY_
ID
PK,FK2

ACT_RET_
DATE

System
Date

TITLE_
ID
PK,FK2

System Date
+ 2 days
MEMBER

DATE

EXP_RET_
DATE

MEMBER_I
D
NUMBER

TITLE_
COPY
COPY_
ID
NUMBER

10

10

TITLE_
COPY
TITLE_ID
DATE

DATE

NUMBER
10

CREATE TABLE rental
(book_date
DATE DEFAULT SYSDATE,
member_id
NUMBER(10)
CONSTRAINT rental_member_id_fk
REFERENCES member(member_id),
copy_id NUMBER(10),
act_ret_date DATE,
exp_ret_date DATE DEFAULT SYSDATE + 2,
title_id
NUMBER(10),
CONSTRAINT rental_book_date_copy_title_ pk
PRIMARY KEY (book_date, member_id,
copy_id,title_id),
CONSTRAINT rental_copy_id_title_id_ fk
FOREIGN KEY (copy_id, title_id)
REFERENCES title_copy(copy_id, title_id));

Introduction to Oracle9i: SQL A-41

Practice 14 Solutions (continued)
e. Table name: RESERVATION

Column
Name
Key
Type
Null/
Unique
FK Ref
Table
FK Ref
Column
Data Type
Length

RES_
DATE

MEMBER_
ID

TITLE_
ID

PK

PK,FK1

PK,FK2

NN,U

NN,U

NN

MEMBER

TITLE

MEMBER_ID

TITLE_ID

NUMBER

NUMBER

10

10

DATE

CREATE TABLE reservation
(res_date
DATE,
member_id
NUMBER(10)
CONSTRAINT reservation_member_id
REFERENCES member(member_id),
title_id
NUMBER(10)
CONSTRAINT reservation_title_id
REFERENCES title(title_id),
CONSTRAINT reservation_resdate_mem_tit_pk PRIMARY KEY
(res_date, member_id, title_id));

Introduction to Oracle9i: SQL A-42

Practice 14 Solutions (continued)
2. Verify that the tables and constraints were created properly by checking the data dictionary.
SELECT
FROM
WHERE

table_name
user_tables
table_name IN ('MEMBER', 'TITLE', 'TITLE_COPY',
'RENTAL', 'RESERVATION');

SELECT
FROM
WHERE

constraint_name, constraint_type, table_name
user_constraints
table_name IN ('MEMBER', 'TITLE', 'TITLE_COPY',
'RENTAL', 'RESERVATION');

3. Create sequences to uniquely identify each row in the MEMBER table and the TITLE table.
a. Member number for the MEMBER table: start with 101; do not allow caching of the
values. Name the sequence MEMBER_ID_SEQ.
CREATE SEQUENCE member_id_seq
START WITH 101
NOCACHE;
b. Title number for the TITLE table: start with 92; no caching. Name the sequence
TITLE_ID_SEQ.
CREATE SEQUENCE title_id_seq
START WITH 92
NOCACHE;
c. Verify the existence of the sequences in the data dictionary.
SELECT
FROM
WHERE

sequence_name, increment_by, last_number
user_sequences
sequence_name IN ('MEMBER_ID_SEQ', 'TITLE_ID_SEQ ');

Introduction to Oracle9i: SQL A-43

Practice 14 Solutions (continued)
4. Add data to the tables. Create a script for each set of data to add.
a. Add movie titles to the TITLE table. Write a script to enter the movie information. Save the
statements in a script named lab14_4a.sql. Use the sequences to uniquely identify each
title. Enter the release dates in the DD-MON-YYYY format. Remember that single quotation
marks in a character field must be specially handled. Verify your additions.
SET ECHO OFF
INSERT INTO title(title_id, title, description, rating,
category, release_date)
VALUES (title_id_seq.NEXTVAL, 'Willie and Christmas Too',
'All of Willie''s friends make a Christmas list for
Santa, but Willie has yet to add his own wish list.',
'G', 'CHILD', TO_DATE('05-OCT-1995','DD-MON-YYYY')
/
INSERT INTO title(title_id , title, description, rating,
category, release_date)
VALUES (title_id_seq.NEXTVAL, 'Alien Again', 'Yet another
installment of science fiction history. Can the
heroine save the planet from the alien life form?',
'R', 'SCIFI', TO_DATE( '19-MAY-1995','DD-MON-YYYY'))
/
INSERT INTO title(title_id, title, description, rating,
category, release_date)
VALUES (title_id_seq.NEXTVAL, 'The Glob', 'A meteor crashes
near a small American town and unleashes carnivorous
goo in this classic.', 'NR', 'SCIFI',
TO_DATE( '12-AUG-1995','DD-MON-YYYY'))
/
INSERT INTO title(title_id, title, description, rating,
category, release_date)
VALUES (title_id_seq.NEXTVAL, 'My Day Off', 'With a little
luck and a lot ingenuity, a teenager skips school for
a day in New York.', 'PG', 'COMEDY',
TO_DATE( '12-JUL-1995','DD-MON-YYYY'))
/
...
COMMIT
/
SET ECHO ON
SELECT
FROM

title
title;

Introduction to Oracle9i: SQL A-44

Practice 14 Solutions (continued)

Title

Description

Rating

Category

Release_date

Willie and
Christmas
Too

All of Willie’s friends
make a Christmas list for
Santa, but Willie has yet to
add his own wish list.

G

CHILD

05-OCT-1995

Alien Again

Yet another installation of
science fiction history. Can
the heroine save the planet
from the alien life form?

R

SCIFI

19-MAY-1995

The Glob

A meteor crashes near a
small American town and
unleashes carnivorous goo
in this classic.

NR

SCIFI

12-AUG-1995

My Day Off

With a little luck and a lot
of ingenuity, a teenager
skips school for a day in
New York

PG

COMEDY

12-JUL-1995

Miracles on
Ice

A six-year-old has doubts
about Santa Claus, but she
discovers that miracles
really do exist.

PG

DRAMA

12-SEP-1995

Soda Gang

After discovering a cache
of drugs, a young couple
find themselves pitted
against a vicious gang.

NR

ACTION

01-JUN-1995

Introduction to Oracle9i: SQL A-45

Practice 14 Solutions (continued)
b. Add data to the MEMBER table. Place the insert statements in a script named
lab14_4b.sql. Execute commands in the script. Be sure to use the sequence to add the
member numbers.
First_
Name

Last_Name

Address

Carmen

Velasquez

LaDoris

City

Phone

Join_Date

283 King Street Seattle

206-899-6666

08-MAR-1990

Ngao

5 Modrany

Bratislava

586-355-8882

08-MAR-1990

Midori

Nagayama

68 Via Centrale Sao Paolo

254-852-5764

17-JUN-1991

Mark

Quick-toSee

6921 King
Way

Lagos

63-559-7777

07-APR-1990

Audry

Ropeburn

86 Chu Street

Hong Kong

41-559-87

18-JAN-1991

Molly

Urguhart

3035 Laurier

Quebec

418-542-9988

18-JAN-1991

SET ECHO OFF
SET VERIFY OFF
INSERT INTO member(member_id, first_name, last_name, address,
city, phone, join_date)
VALUES (member_id_seq.NEXTVAL, '&first_name', '&last_name',
'&address', '&city', '&phone', TO_DATE('&join_date',
'DD-MM-YYYY');
COMMIT;
SET VERIFY ON
SET ECHO ON

Introduction to Oracle9i: SQL A-46

Practice 14 Solutions (continued)
c. Add the following movie copies in the TITLE_COPY table:
Note: Have the TITLE_ID numbers available for this exercise.

Title
Willie and Christmas Too
Alien Again
The Glob
My Day Off

Miracles on Ice
Soda Gang

Copy_Id
1
1
2
1
1
2
3
1
1

Status
AVAILABLE
AVAILABLE
RENTED
AVAILABLE
AVAILABLE
AVAILABLE
RENTED
AVAILABLE
AVAILABLE

INSERT INTO title_copy(copy_id, title_id, status)
VALUES (1, 92, 'AVAILABLE');
INSERT INTO title_copy(copy_id, title_id, status)
VALUES (1, 93, 'AVAILABLE');
INSERT INTO title_copy(copy_id, title_id, status)
VALUES (2, 93, 'RENTED');
INSERT INTO title_copy(copy_id, title_id, status)
VALUES (1, 94, 'AVAILABLE');
INSERT INTO title_copy(copy_id, title_id, status)
VALUES (1, 95, 'AVAILABLE');
INSERT INTO title_copy(copy_id, title_id,status)
VALUES (2, 95, 'AVAILABLE');
INSERT INTO title_copy(copy_id, title_id,status)
VALUES (3, 95, 'RENTED');
INSERT INTO title_copy(copy_id, title_id,status)
VALUES (1, 96, 'AVAILABLE');
INSERT INTO title_copy(copy_id, title_id,status)
VALUES (1, 97, 'AVAILABLE');

Introduction to Oracle9i: SQL A-47

Practice 14 Solutions (continued)
d. Add the following rentals to the RENTAL table:
Note: Title number may be different depending on sequence number.

Title_
Id

Copy_
Id

Member_
Id

Book_date

Exp_Ret_Date

Act_Ret_Date

92

1

101

3 days ago

1 day ago

2 days ago

93

2

101

1 day ago

1 day from now

95

3

102

2 days ago

Today

97

1

106

4 days ago

2 days ago

2 days ago

INSERT INTO rental(title_id, copy_id, member_id,
book_date, exp_ret_date, act_ret_date)
VALUES (92, 1, 101, sysdate-3, sysdate-1, sysdate-2);
INSERT INTO rental(title_id, copy_id, member_id,
book_date, exp_ret_date, act_ret_date)
VALUES (93, 2, 101, sysdate-1, sysdate-1, NULL);
INSERT INTO rental(title_id, copy_id, member_id,
book_date, exp_ret_date, act_ret_date)
VALUES (95, 3, 102, sysdate-2, sysdate, NULL);
INSERT INTO rental(title_id, copy_id, member_id,
book_date, exp_ret_date,act_ret_date)
VALUES (97, 1, 106, sysdate-4, sysdate-2, sysdate-2);
COMMIT;

Introduction to Oracle9i: SQL A-48

Practice 14 Solutions (continued)
5. Create a view named TITLE_AVAIL to show the movie titles and the availability of
each copy and its expected return date if rented. Query all rows from the view. Order the results by
title.
CREATE VIEW title_avail AS
SELECT
t.title, c.copy_id, c.status, r.exp_ret_date
FROM
title t, title_copy c, rental r
WHERE
t.title_id = c.title_id
AND
c.copy_id = r.copy_id(+)
AND
c.title_id = r.title_id(+);
SELECT
*
FROM
title_avail
ORDER BY title, copy_id;
6. Make changes to data in the tables.
a. Add a new title. The movie is “Interstellar Wars,” which is rated PG and classified as a
scifi movie. The release date is 07-JUL-77. The description is “Futuristic interstellar
action movie. Can the rebels save the humans from the evil empire?” Be sure to add a title
copy record for two copies.
INSERT INTO title(title_id, title, description, rating,
category, release_date)
VALUES (title_id_seq.NEXTVAL, 'Interstellar Wars',
'Futuristic interstellar action movie. Can the
rebels save the humans from the evil Empire?',
'PG', 'SCIFI', '07-JUL-77');
INSERT INTO title_copy (copy_id, title_id, status)
VALUES (1, 98, 'AVAILABLE');
INSERT INTO title_copy (copy_id, title_id, status)
VALUES (2, 98, 'AVAILABLE');
b. Enter two reservations. One reservation is for Carmen Velasquez, who wants to rent
“Interstellar Wars.” The other is for Mark Quick-to-See, who wants to rent “Soda Gang.”
INSERT
VALUES
INSERT
VALUES

INTO reservation (res_date, member_id, title_id)
(SYSDATE, 101, 98);
INTO reservation (res_date, member_id, title_id)
(SYSDATE, 104, 97);

Introduction to Oracle9i: SQL A-49

Practice 14 Solutions (continued)
c. Customer Carmen Velasquez rents the movie “Interstellar Wars,” copy 1. Remove her
reservation for the movie. Record the information about the rental. Allow the default
value for the expected return date to be used. Verify that the rental was recorded by using
the view you created.
INSERT
VALUES
UPDATE
SET
WHERE
AND
DELETE
FROM
WHERE

INTO rental(title_id, copy_id, member_id)
(98,1,101);
title_copy
status= 'RENTED'
title_id = 98
copy_id = 1;
reservation
member_id = 101;

SELECT
*
FROM
title_avail
ORDER BY title, copy_id;
7. Make a modification to one of the tables.
a. Add a PRICE column to the TITLE table to record the purchase price of the video. The
column should have a total length of eight digits and two decimal places. Verify your
modifications.
ALTER TABLE title
ADD (price NUMBER(8,2));
DESCRIBE title

Introduction to Oracle9i: SQL A-50

Practice 14 Solutions (continued)
b. Create a script named lab14_7b.sql that contains update statements that update each
video with a price according to the following list. Run the commands in the script.
Note: Have the TITLE_ID numbers available for this exercise.

Title

Price

Willie and Christmas Too
Alien Again
The Glob
My Day Off
Miracles on Ice
Soda Gang
Interstellar Wars

25
35
35
35
30
35
29

SET ECHO OFF
SET VERIFY OFF
DEFINE price=
DEFINE title_id=
UPDATE title
SET
price = &price
WHERE title_id = &title_id;
SET VERIFY OFF
SET ECHO OFF
c.

Ensure that in the future all titles contain a price value. Veri fy the constraint.
ALTER TABLE title
MODIFY (price CONSTRAINT title_price_ nn NOT NULL);
SELECT constraint_name, constraint_type,
search_condition
FROM
user_constraints
WHERE
table_name = 'TITLE';

Introduction to Oracle9i: SQL A-51

Practice 14 Solutions (continued)
8. Create a report titled Customer History Report. This report contains each customer's
history of renting videos. Be sure to include the customer name, movie rented, dates of the
rental, and duration of rentals. Total the number of rentals for all customers for the reporting
period. Save the commands that generate the report in a script file named lab14_8.sql.
SET ECHO OFF
SET VERIFY OFF
TTITLE 'Customer History Report'
BREAK ON member SKIP 1 ON REPORT
SELECT
m.first_name||' '||m.last_name MEMBER, t.title,
r.book_date, r.act_ret_date - r.book_date DURATION
FROM
member m, title t, rental r
WHERE
r.member_id = m.member_id
AND
r.title_id = t.title_id
ORDER BY member;
CLEAR BREAK
TTITLE OFF
SET VERIFY ON
SET ECHO ON

Introduction to Oracle9i: SQL A-52

Practice 15 Solutions
1. List the department IDs for departments that do not contain the job ID ST_CLERK, using SET
operators.
SELECT
FROM
MINUS
SELECT
FROM
WHERE

department_id
departments
department_id
employees
job_id = 'ST_CLERK';

2. Display the country ID and the name of the countries that have no departments located in them,
using SET operators.
SELECT
FROM
MINUS
SELECT
FROM
WHERE

country_id,country_name
countries
l.country_id,c.country_name
locations l,
countries c
l.country_id = c.country_id;

3. Produce a list of jobs for departments 10, 50, and 20, in that order. Display job ID and
department ID, using SET operators.
COLUMN dummy PRINT
SELECT job_id, department_id, 'x' dummy
FROM
employees
WHERE department_id = 10
UNION
SELECT job_id, department_id, 'y'
FROM
employees
WHERE department_id = 50
UNION
SELECT job_id, department_id, 'z'
FROM
employees
WHERE department_id = 20
ORDER BY 3;
COLUMN dummy NOPRINT

Introduction to Oracle9i: SQL A-53

Practice 15 Solutions (continued)
4. List the employee IDs and job IDs of those employees, who are currently in the job title that they
have held once before during their tenure with the company.
SELECT
employee_id,job_id
FROM
employees
INTERSECT
SELECT
employee_id,job_id
FROM
job_history;
5. Write a compond query that lists the following :
•

Last names and department ID of all the employees from the EMPLOYEES table, irrespective
of whether they belong to any department

•

Department ID and department name of all the departments from the DEPARTMENTS table,
irrespective of whether they have employees working in them

SELECT last_name,department_id,TO_CHAR(null)
FROM
employees
UNION
SELECT TO_CHAR(null),department_id,department_name
FROM departments;

Introduction to Oracle9i: SQL A-54

Practice 16 Solutions
1. Alter the session to set the NLS_DATE_FORMAT to DD-MON-YYYY HH24:MI:SS.
ALTER SESSION SET NLS_DATE_FORMAT =
'DD-MON-YYYY HH24:MI:SS';
2. a. Write queries to display the time zone offsets (TZ_OFFSET) for the following time zones.
US/Pacific-New
SELECT TZ_OFFSET ('US/Pacific-New') from dual;
Singapore
SELECT TZ_OFFSET ('Singapore') from dual;
Egypt
SELECT TZ_OFFSET ('Egypt') from dual;
b. Alter the session to set the TIME_ZONE parameter value to the time zone offset of
US/Pacific-New.
ALTER SESSION SET TIME_ZONE = '-8:00';
c. Display the CURRENT_DATE, CURRENT_TIMESTAMP, and LOCALTIMESTAMP for this
session.
Note: The output might be different based on the date when the command is executed.
SELECT CURRENT_DATE, CURRENT_TIMESTAMP, LOCALTIMESTAMP
FROM DUAL;
d. Alter the session to set the TIME_ZONE parameter value to the time zone offset of
Singapore.
ALTER SESSION SET TIME_ZONE = '+8:00';
e. Display the CURRENT_DATE, CURRENT_TIMESTAMP, LOCALTIMESTAMP for this
session.
Note: The output might be different based on the date when the command is executed.
SELECT CURRENT_DATE, CURRENT_TIMESTAMP, LOCALTIMESTAMP
FROM DUAL;
3. Write a query to display the DBTIMEZONE and SESSIONTIMEZONE.
SELECT DBTIMEZONE,SESSIONTIMEZONE
FROM DUAL;

Introduction to Oracle9i: SQL A-55

Practice 16 Solutions (continued)
4. Write a query to extract the YEAR from HIRE_DATE column of the EMPLOYEES table for those
employees who work in department 80.
SELECT last_name, EXTRACT (YEAR FROM HIRE_DATE)
FROM employees
WHERE department_id = 80;

Introduction to Oracle9i: SQL A-56

Practice 17 Solutions
1. Write a query to display the following for those employees whose manager ID is less than 120:
–

Manager ID

–

Job ID and total salary for every job ID for employees who report to the same manager

–

Total salary of those managers

–

Total salary of those managers, irrespective of the job IDs

SELECT manager_id,job_id,sum(salary)
FROM
employees
WHERE manager_id < 120
GROUP BY ROLLUP(manager_id,job_id);
2. Observe the output from question 1. Write a query using the GROUPING function to determine
whether the NULL values in the columns corresponding to the GROUP BY expressions are caused by
the ROLLUP operation.
SELECT manager_id MGR ,job_id JOB,
sum(salary),GROUPING(manager_id),GROUPING(job_id)
FROM
employees
WHERE manager_id < 120
GROUP BY ROLLUP(manager_id,job_id);
3. Write a query to display the following for those employees whose manager ID is
less than 120 :
–

Manager ID

–

Job and total salaries for every job for employees who report to the same manager

–

Total salary of those managers

–

Cross-tabulation values to display the total salary for every job, irrespective of the
manager

–

Total salary irrespective of all job titles

SELECT manager_id, job_id, sum(salary)
FROM
employees
WHERE manager_id < 120
GROUP BY CUBE(manager_id, job_id);

Introduction to Oracle9i: SQL A-57

Practice 17 Solutions (continued)
4. Observe the output from question 3. Write a query using the GROUPING function to determine
whether the NULL values in the columns corresponding to the GROUP BY expressions are
caused by the CUBE operation.
SELECT manager_id MGR ,job_id JOB,
sum(salary),GROUPING(manager_id),GROUPING(job_id)
FROM
employees
WHERE manager_id < 120
GROUP BY CUBE(manager_id,job_id);
5.

Using GROUPING SETS, write a query to display the following groupings :
–

department_id, manager_id, job_id

–

department_id, job_id

–

Manager_id,

job_id

The query should calculate the sum of the salaries for each of these groups.
SELECT department_id, manager_id, job_id, SUM(salary)
FROM employees
GROUP BY
GROUPING SETS ((department_id, manager_id, job_id),
(department_id, job_id),(manager_id,job_id));

Introduction to Oracle9i: SQL A-58

Practice 18 Solutions
1. Write a query to display the last name, department number, and salary of any employee whose
department number and salary both match the department number and salary of any employee who
earns a commission.
SELECT last_name, department_id, salary
FROM
employees
WHERE (salary, department_id) IN
(SELECT salary, department_id
FROM
employees
WHERE
commission_pct IS NOT NULL);
2. Display the last name, department name, and salary of any employee whose salary and commission
match the salary and commission of any employee located in location ID1700.
SELECT last_name, department_name, salary
FROM
employees e, departments d
WHERE e.department_id = d.department_id
AND
(salary, NVL(commission_pct,0)) IN
(SELECT salary, NVL(commission_pct,0)
FROM
employees e, departments d
WHERE
e.department_id = d.department_id
AND
d.location_id = 1700);
3. Create a query to display the last name, hire date, and salary for all employees who have the same
salary and commission as Kochhar.
Note: Do not display Kochhar in the result set.
SELECT last_name, hire_date, salary
FROM
employees
WHERE (salary, NVL(commission_pct,0)) IN
(SELECT salary, NVL(commission_pct,0)
FROM
employees
WHERE last_name = 'Kochhar')
AND last_name != 'Kochhar';
4. Create a query to display the employees who earn a salary that is higher than the salary of
all of the sales managers (JOB_ID = 'SA_MAN'). Sort the results on salary from highest to
lowest.
SELECT last_name, job_id, salary
FROM
employees
WHERE salary > ALL
(SELECT salary
FROM
employees
WHERE job_id = 'SA_MAN')
ORDER BY salary DESC;

Introduction to Oracle9i: SQL A-59

Practice 18 Solutions (continued)
5. Display the details of the employee ID, last name, and department ID of those employees who live
in cities whose name begins with T.
SELECT employee_id, last_name, department_id
FROM
employees
WHERE department_id IN (SELECT department_id
FROM departments
WHERE location_id IN
(SELECT location_id
FROM locations
WHERE city LIKE 'T%'));
6. Write a query to find all employees who earn more than the average salary in their departments.
Display last name, salary, department ID, and the average salary for the department. Sort by average
salary. Use alises for the columns retrieved by the query as shown in the sample output.
SELECT e.last_name ename, e.salary salary,
e.department_id deptno, AVG(a.salary) dept_ avg
FROM
employees e, employees a
WHERE
e.department_id = a.department_id
AND
e.salary > (SELECT AVG(salary)
FROM
employees
WHERE department_id = e.department_ id )
GROUP BY e.last_name, e.salary, e.department_id
ORDER BY AVG(a.salary);
7. Find all employees who are not supervisors.
a. First do this by using the NOT EXISTS operator.
SELECT outer.last_name
FROM
employees outer
WHERE NOT EXISTS (SELECT 'X'
FROM employees inner
WHERE inner.manager_id =
outer.employee_id);

Introduction to Oracle9i: SQL A-60

Practice 18 Solutions (continued)
b. Can this be done by using the NOT IN operator? How, or why not?
SELECT
FROM
WHERE
NOT IN

outer.last_name
employees outer
outer.employee_id
(SELECT inner.manager_id
FROM
employees inner);
This alternative solution is not a good one. The subquery picks up a NULL value, so the entire
query returns no rows. The reason is that all conditions that compare a NULL value result in
NULL. Whenever NULL values are likely to be part of the value set, do not use NOT IN as a
substitute for NOT EXISTS.
8. Write a query to display the last names of the employees who earn less than the average salary in
their departments.
SELECT last_name
FROM
employees outer
WHERE outer.salary < (SELECT AVG(inner.salary)
FROM employees inner
WHERE inner.department_id
= outer.department_id);
9. Write a query to display the last names who have one or more coworkers in their departments with
later hire dates but higher salaries.
SELECT last_name
FROM
employees outer
WHERE EXISTS (SELECT 'X'
FROM employees inner
WHERE inner.department_id =
outer.department_id
AND inner.hire_date > outer.hire_date
AND inner.salary > outer.salary);
10. Write a query to display the employee ID, last names of the employees, and department names of all
employees.
Note: Use a scalar subquery to retrieve the department name in the SELECT statement.
SELECT employee_id, last_name,
(SELECT department_name
FROM departments d
WHERE
e.department_id =
d.department_id ) department
FROM employees e
ORDER BY department;

Introduction to Oracle9i: SQL A-61

Practice 18 Solutions (continued)
11. Write a query to display the department names of those departments whose total salary cost is above
one-eighth (1/8) of the total salary cost of the whole company. Use the WITH clause to write this
query. Name the query SUMMARY.
WITH
summary AS (
SELECT department_name, SUM(salary) AS dept_total
FROM employees, departments
WHERE employees.department_id =
departments.department_id
GROUP BY department_name)
SELECT department_name, dept_total
FROM summary
WHERE dept_total > (
SELECT SUM(dept_total) * 1/8
FROM summary)
ORDER BY dept_total DESC;

Introduction to Oracle9i: SQL A-62

Practice 19 Solutions
1. Look at the following output. Is this output the result of a hierarchical query? Explain why or why
not.
a.

Exhibit 1: This is not a hierarchical query; the report simply has a descending sort
on SALARY.
Exhibit 2: This is not a hierarchical query; there are two tables involved.
Exhibit 3: Yes, this is most definitely a hierarchical query as it displays the tree
structure representing the management reporting line from the EMPLOYEES table.

2. Produce a report showing an organization chart for Mourgos’s department. Print last names, salaries,
and department IDs.
SELECT last_name, salary, department_id
FROM employees
START WITH last_name = 'Mourgos'
CONNECT BY PRIOR employee_id = manager_id;
3. Create a report that shows the hierarchy of the managers for the employee Lorentz. Display his
immediate manager first.
SELECT last_name
FROM employees
WHERE last_name != 'Lorentz'
START WITH last_name = 'Lorentz'
CONNECT BY PRIOR manager_id = employee_id;
4. Create an indented report showing the management hierarchy starting from the employee whose
LAST_NAME is Kochhar. Print the employee’s last name, manager ID, and department ID. Give alias
names to the columns as shown in the sample output.
COLUMN name FORMAT A20
SELECT LPAD(last_name, LENGTH(last_name)+(LEVEL*2) -2,'_')
name,manager_id mgr, department_id deptno
FROM employees
START WITH last_name = 'Kochhar'
CONNECT BY PRIOR employee_id = manager_id
/
COLUMN name CLEAR

Introduction to Oracle9i: SQL A-63

Practice 19 Solutions (continued)
If you have time, complete the following exercises:
5. Produce a company organization chart that shows the management hierarchy. Start with the person at
the top level, exclude all people with a job ID of IT_PROG, and exclude De Haan and those
employees who report to De Hann.
SELECT last_name,employee_id, manager_id
FROM
employees
WHERE job_id != 'IT_PROG'
START WITH manager_id IS NULL
CONNECT BY PRIOR employee_id = manager_id
AND last_name != 'De Haan';

Introduction to Oracle9i: SQL A-64

Practice 20 Solutions
1. Run the cre_sal_history.sql script in the Labs folder to create the SAL_HISTORY table.
@ \Labs\cre_sal_history.sql
2. Display the structure of the SAL_HISTORY table.
DESC sal_history
3. Run the cre_mgr_history.sql script in the Labs folder to create the MGR_HISTORY table.
@ \Labs\cre_mgr_history.sql
4. Display the structure of the MGR_HISTORY table.
DESC mgr_history
5. Run the cre_special_sal.sql script in the Labs folder to create the SPECIAL_SAL table.
@ \Labs\cre_special_sal.sql
6. Display the structure of the SPECIAL_SAL table.
DESC special_sal
7. a. Write a query to do the following:
–

Retrieve the details of the employee ID, hire date, salary, and manager ID of those employees
whose employee ID is less than 125 from the EMPLOYEES table.

–

If the salary is more than $20,000, insert the details of employee ID and salary into the
SPECIAL_SAL table.

–

Insert the details of the employee ID, hire date, and salary into the SAL_HISTORY table.

–

Insert the details of the employee ID, manager ID, and SYSDATE into the MGR_HISTORY
table.

INSERT ALL
WHEN SAL > 20000 THEN
INTO special_empsal VALUES (EMPID, SAL)
ELSE
INTO sal_history VALUES(EMPID,HIREDATE,SAL)
INTO mgr_history VALUES(EMPID,MGR,SAL)
SELECT employee_id EMPID, hire_date HIREDATE,
salary SAL, manager_id MGR
FROM employees
WHERE employee_id < 125;

Introduction to Oracle9i: SQL A-65

Practice 20 Solutions (continued)
b. Display the records from the SPECIAL_SAL table.
SELECT * FROM

special_sal;

c. Display the records from the SAL_HISTORY table.
SELECT * FROM

sal_history;

d. Display the records from the MGR_HISTORY table.
SELECT * FROM mgr_history;
8. a. Run the cre_sales_source_data.sql script in the Labs folder to create the
SALES_SOURCE_DATA table.
@ \Labs\cre_sales_source_data.sql
b. Run the ins_sales_source_data.sql script in the Labs folder to insert records into the
SALES_SOURCE_DATA table.
@ \Labs\ins_sales_source_data.sql
c. Display the structure of the SALES_SOURCE_DATA table.
DESC sales_source_data
d. Display the records from the SALES_SOURCE_DATA table.
SELECT * FROM SALES_SOURCE_DATA;
e. Run the cre_sales_info.sql script in the Labs folder to create the SALES_INFO table.
@ \Labs\cre_sales_info.sql
f. Display the structure of the SALES_INFO table.
DESC sales_info
g. Write a query to do the following:
–

Retrieve the details of the employee ID, week ID, sales on Monday, sales on Tuesday, sales
on Wednesday, sales on Thursday, and sales on Friday from the SALES_SOURCE_DATA
table.

–

Build a transformation such that each record retrieved from the SALES_SOURCE_DATA
table is converted into multiple records for the SALES_INFO table.

Hint: Use a pivoting INSERT statement.

Introduction to Oracle9i: SQL A-66

Practice 20 Solutions (continued)
INSERT ALL
INTO sales_info VALUES (employee_id, week_id, sales_MON)
INTO sales_info VALUES (employee_id, week_id, sales_TUE)
INTO sales_info VALUES (employee_id, week_id, sales_WED)
INTO sales_info VALUES (employee_id, week_id, sales_THUR)
INTO sales_info VALUES (employee_id, week_id, sales_FRI)
SELECT EMPLOYEE_ID, week_id, sales_MON, sales_TUE,
sales_WED, sales_THUR,sales_FRI FROM sales_source_data;
h. Display the records from the SALES_INFO table.
SELECT * FROM sales_info;
9. a. Create the DEPT_NAMED_INDEX table based on the following table instance chart. Name the
index for the PRIMARY KEY column as DEPT_PK_IDX.

COLUMN Name

Deptno

Dname

Primary Key

Yes

Data type

Number

VARCHAR2

Length

4

30

CREATE TABLE DEPT_NAMED_INDEX
(deptno NUMBER(4)
PRIMARY KEY USING INDEX
(CREATE INDEX dept_pk_idx ON
DEPT_NAMED_INDEX(deptno)),
dname VARCHAR2(30));
b. Query the USER_INDEXES table to display the INDEX_NAME for the
DEPT_NAMED_INDEX table.
SELECT INDEX_NAME, TABLE_NAME
FROM USER_INDEXES
WHERE TABLE_NAME = 'DEPT_NAMED_INDEX';

Introduction to Oracle9i: SQL A-67

Practice D Solutions
1. Write a script to describe and select the data from your tables. Use CHR(10) in the select list with
the concatenation operator ( || ) to generate a line feed in your report Save the output of the script
into my_file1.sql. To save the file, select the SAVE option for the output, and execute the code.
Remember to save the file with a .sql extension. To execute the my_file1.sql, browse to
locate the script, load the script, and execute the script.
SET PAGESIZE 0
SELECT

'DESC ' || table_name || CHR(10) ||
'SELECT * FROM ' || table_name || ';'
user_tables

FROM
/
SET PAGESIZE 24
SET LINESIZE 100

2. Use SQL to generate SQL statements that revoke user privileges. Use the data dictionary views
USER_TAB_PRIVS_MADE and USER_COL_PRIVS_MADE.
a. Execute the script \Labs\privs.sql to grant privileges to the user SYSTEM.
b. Query the data dictionary views to check the privileges. In the sample output shown, note that
the data in the GRANTOR column can vary depending on who the GRANTOR is. Also the last
column that has been truncated is the GRANTABLE column.
COLUMN
COLUMN
COLUMN
COLUMN
COLUMN
SELECT
FROM
WHERE
SELECT
FROM
WHERE

grantee
FORMAT A10
table_name
FORMAT A10
column_name FORMAT A10
grantor
FORMAT A10
privilege
FORMAT A10
*
user_tab_privs_made
grantee = 'SYSTEM';
*
user_col_privs_made
grantee = 'SYSTEM';

Introduction to Oracle9i: SQL A-68

Practice D Solutions (continued)
c. Produce a script to revoke the privileges. Save the output of the script into my_file2.sql. To
save the file, select the SAVE option for the output, and execute the code. Remember to save the
file with a .sql extension. To execute the my_file2.sql, browse to locate the script, load the
script, and execute the script.
SET VERIFY OFF
SET PAGESIZE 0
SELECT
'REVOKE ' || privilege || ' ON ' ||
table_name || ' FROM system;'
FROM
user_tab_privs_made
WHERE grantee = 'SYSTEM'
/
SELECT
DISTINCT
'REVOKE ' || privilege || ' ON ' ||
table_name || ' FROM system;'
FROM
user_col_privs_made
WHERE grantee = 'SYSTEM'
/

SET VERIFY ON
SET PAGESIZE 24

Introduction to Oracle9i: SQL A-69

Introduction to Oracle9i: SQL A-70

Table Descriptions
and Data

COUNTRIES Table
DESCRIBE countries

SELECT * FROM countries;

Introduction Oracle9i: SQL B-3

DEPARTMENTS Table
DESCRIBE departments

SELECT * FROM departments;

Introduction Oracle9i: SQL B-4

EMPLOYEES Table
DESCRIBE employees

SELECT * FROM employees;

Continued on next page
Introduction Oracle9i: SQL B-5

EMPLOYEES Table (continued)

Introduction Oracle9i: SQL B-6

JOBS Table
DESCRIBE jobs

SELECT * FROM jobs;

Introduction Oracle9i: SQL B-7

JOB_GRADES Table
DESCRIBE job_grades

SELECT * FROM job_grades;

Introduction Oracle9i: SQL B-8

JOB_HISTORY Table
DESCRIBE job_history

SELECT * FROM job_history;

Introduction Oracle9i: SQL B-9

LOCATIONS Table
DESCRIBE locations

SELECT * FROM locations;

Introduction Oracle9i: SQL B-10

REGIONS Table
DESCRIBE regions

SELECT * FROM regions;

Introduction Oracle9i: SQL B-11

Introduction Oracle9i: SQL B-12

Using SQL*Plus

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this appendix, you should be able to
do the following:

•
•
•
•

C-2

Log in to SQL*Plus
Edit SQL commands
Format output using SQL*Plus commands
Interact with script files

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
You may want to create SELECT statements that can be used again and again. This lesson also covers the
use of SQL*Plus commands to execute SQL statements. You learn how to format output using SQL*Plus
commands, edit SQL commands, and save scripts in SQL*Plus.

Introduction to Oracle9i: SQL C-2

SQL and SQL*Plus Interaction
SQL statements

Server
SQL*Plus
Query results

Buffer

SQL
scripts
C-3

Copyright © Oracle Corporation, 2001. All rights reserved.

SQL and SQL*Plus
SQL is a command language for communication with the Oracle9i Server from any tool or application.
Oracle SQL contains many extensions. When you enter a SQL statement, it is stored in a part of memory
called the SQL buffer and remains there until you enter a new SQL statement.
SQL*Plus is an Oracle tool that recognizes and submits SQL statements to the Oracle9i Server for
execution. It contains its own command language.
Features of SQL
•

SQL can be used by a range of users, including those with little or no programming
experience.

•

It is a nonprocedural language.

•

It reduces the amount of time required for creating and maintaining systems.

•

It is an English-like language.

Features of SQL*Plus
•

SQL*Plus accepts ad hoc entry of statements.

•
•

It accepts SQL input from files.
It provides a line editor for modifying SQL statements.

•
•

It controls environmental settings.
It formats query results into basic reports.

•

It accesses local and remote databases.
Introduction to Oracle9i: SQL C-3

SQL Statements versus SQL*Plus
Commands
SQL
• A language
• ANSI standard
• Keywords cannot be
abbreviated
• Statements manipulate
data and table
definitions in the
database
SQL
statements

C-4

SQL
buffer

SQL*Plus
• An environment
• Oracle proprietary
• Keywords can be
abbreviated
• Commands do not
allow manipulation of
values in the database

SQL*Plus
commands

SQL*Plus
buffer

Copyright © Oracle Corporation, 2001. All rights reserved.

SQL and SQL*Plus (continued)
The following table compares SQL and SQL*Plus:
SQL
Is a language for communicating with the Oracle
Server to access data
Is based on American National Standards
Institute (ANSI) standard SQL

SQL*Plus
Recognizes SQL statements and sends them to
the server
Is the Oracle proprietary interface for executing
SQL statements

Manipulates data and table definitions in the
database

Does not allow manipulation of values in the
database

Is entered into the SQL buffer on one or more
lines

Is entered one line at a time, not stored in the
SQL buffer

Does not have a continuation character

Uses a dash (-) as a continuation character if the
command is longer than one line

Cannot be abbreviated

Can be abbreviated

Uses a termination character to execute
commands immediately

Does not require termination characters;
executes commands immediately

Uses functions to perform some formatting

Uses commands to format data

Introduction to Oracle9i: SQL C-4

Overview of SQL*Plus
•
•
•
•
•

Log in to SQL*Plus.

•
•

Execute saved files.

Describe the table structure.
Edit your SQL statement.
Execute SQL from SQL*Plus.
Save SQL statements to files and append SQL
statements to files.
Load commands from file to buffer
to edit.

C-5

Copyright © Oracle Corporation, 2001. All rights reserved.

SQL*Plus
SQL*Plus is an environment in which you can do the following:
•

Execute SQL statements to retrieve, modify, add, and remove data from the database

•

Format, perform calculations on, store, and print query results in the form of reports

•

Create script files to store SQL statements for repetitive use in the future

SQL*Plus commands can be divided into the following main categories:
Category
Environment
Format
File manipulation
Execution
Edit
Interaction
Miscellaneous

Purpose
Affect the general behavior of SQL statements for the session
Format query results
Save, load, and run script files
Send SQL statements from SQL buffer to the Oracle Server
Modify SQL statements in the buffer
Create and pass variables to SQL statements, print variable values, and
print messages to the screen
Connect to the database, manipulate the SQL*Plus environment, and
display column definitions

Introduction to Oracle9i: SQL C-5

Logging In to SQL*Plus
•

From a Windows environment:

•

From a command line:
sqlplus [username[/password
[@database]]]

Copyright © Oracle Corporation, 2001. All rights reserved.

C-6

Logging In to SQL*Plus
How you invoke SQL*Plus depends on which type of operating system or Windows environment you are
running.
To log in through a Windows environment:
1. Select Start > Programs > Oracle for Windows NT > SQL*Plus.
2. Enter the username, password, and database name.
To log in through a command line environment:
1. Log on to your machine.
2. Enter the SQL*Plus command shown in the slide.
In the syntax:
username

your database username.

password

your database password (if you enter your password here, it is visible.)

@database

the database connect string.

Note: To ensure the integrity of your password, do not enter it at the operating system prompt. Instead,
enter only your username. Enter your password at the Password prompt.
After you log in to SQL*Plus, you see the following message (if you are using SQL*Plus version 9i):
SQL*Plus: Release 9.0.1.0.0 - Development on Tue Jan 9 08:44:28 2001
(c) Copyright 2000 Oracle Corporation. All rights reserved.
Introduction to Oracle9i: SQL C-6

Displaying Table Structure

Use the SQL*Plus DESCRIBE command to display the
structure of a table.
DESC[RIBE] tablename

C-7

Copyright © Oracle Corporation, 2001. All rights reserved.

Displaying Table Structure
In SQL*Plus you can display the structure of a table using the DESCRIBE command. The result of the
command is a display of column names and data types as well as an indication if a column must contain
data.
In the syntax:
tablename

the name of any existing table, view, or synonym that is accessi ble to the
user

To describe the JOB_GRADES table, use this command:
SQL> DESCRIBE job_grades
Name
Null?
----------------------------------------- -------GRADE_LEVEL
LOWEST_SAL
HIGHEST_SAL

Introduction to Oracle9i: SQL C-7

Type
----------VARCHAR2 (3)
NUMBER
NUMBER

Displaying Table Structure
SQL> DESCRIBE departments

Name
----------------------DEPARTMENT_ID
DEPARTMENT_NAME
MANAGER_ID
LOCATION_ID

Null?
Type
-------- -----------NOT NULL NUMBER(4)
NOT NULL VARCHAR2(30)
NUMBER(6)
NUMBER(4)

Copyright © Oracle Corporation, 2001. All rights reserved.

C-8

Displaying Table Structure (continued)
The example in the slide displays the information about the structure of the DEPARTMENTS table.
In the result:
Null?

specifies whether a column must contain data; NOT NULL indicates that a
column must contain data

Type

displays the data type for a column

The following table describes the data types:
Data type
NUMBER(p,s)

Description
Number value that has a maximum number of digits p , the number
of digits to the right of the decimal point s

VARCHAR2(s)
DATE

Variable-length character value of maximum size s
Date and time value between January 1, 4712 B.C., and A.D.
December 31, 9999

CHAR(s)

Fixed-length character value of size s

Introduction to Oracle9i: SQL C-8

SQL*Plus Editing Commands
•
•
•
•
•
•
•

C-9

A[PPEND] text
C[HANGE] / old / new
C[HANGE] / text /
CL[EAR] BUFF[ER]
DEL
DEL n
DEL m n

Copyright © Oracle Corporation, 2001. All rights reserved.

SQL*Plus Editing Commands
SQL*Plus commands are entered one line at a time and are not stored in the SQL buffer.
Command
A[PPEND] text
C[HANGE] / old / new
C[HANGE] / text /
CL[EAR] BUFF[ER]
DEL
DEL n
DEL m n

Description
Adds text to the end of the current line
Changes old text to new in the current line
Deletes text from the current line
Deletes all lines from the SQL buffer
Deletes current line
Deletes line n
Deletes lines m to n inclusive

Guidelines
•

If you press [Enter] before completing a command, SQL*Plus prompts you with a line number.

•

You terminate the SQL buffer either by entering one of the terminator characters (semicolon or slash)
or by pressing [Enter] twice. The SQL prompt then appears.

Introduction to Oracle9i: SQL C-9

SQL*Plus Editing Commands
•
•
•
•
•
•
•
•
•

I[NPUT]
I[NPUT] text
L[IST]
L[IST] n
L[IST] m n
R[UN]
n
n text
0 text

C-10

Copyright © Oracle Corporation, 2001. All rights reserved.

SQL*Plus Editing Commands (continued)
Command
I[NPUT]
I[NPUT] text
L[IST]
L[IST] n
L[IST] m n
R[UN]
n
n text
0 text

Description
Inserts an indefinite number of lines
Inserts a line consisting of text
Lists all lines in the SQL buffer
Lists one line (specified by n)
Lists a range of lines (m to n) inclusive
Displays and runs the current SQL statement in the buffer
Specifies the line to make the current line
Replaces line n with text
Inserts a line before line 1

Note: You can enter only one SQL*Plus command per SQL prompt. SQL*Plus commands are not stored
in the buffer. To continue a SQL*Plus command on the next line, end the first line with a hyphen (-).

Introduction to Oracle9i: SQL C-10

Using LIST, n, and APPEND
SQL> LIST
1 SELECT last_name
2* FROM
employees
SQL> 1
1* SELECT last_name
SQL> A , job_id
1* SELECT last_name, job_id
SQL> L
1 SELECT last_name, job_id
2* FROM
employees

C-11

Copyright © Oracle Corporation, 2001. All rights reserved.

Using LIST, n, and APPEND
•

Use the L[IST] command to display the contents of the SQL buffer. The * beside line 2 in the
buffer indicates that line 2 is the current line. Any edits that you made apply to the current line.

•

Change the number of the current line by entering the number of the line you want to edit. The new
current line is displayed.

•

Use the A[PPEND] command to add text to the current line. The newly edited line is displayed.
Verify the new contents of the buffer by using the LIST command.

Note: Many SQL*Plus commands including LIST and APPEND can be abbreviated to just their first letter.
LIST can be abbreviated to L, APPEND can be abbreviated to A.

Introduction to Oracle9i: SQL C-11

Using the CHANGE Command

SQL> L
1* SELECT * from employees
SQL> c/employees/departments
1* SELECT * from departments
SQL> L
1* SELECT * from departments

C-12

Copyright © Oracle Corporation, 2001. All rights reserved.

Using the CHANGE Command
•

Use L[IST] to display the contents of the buffer

•

Use the C[HANGE] command to alter the contents of the current line in the SQL buffer. In this case,
replace the employees table with the departments table. The new current line is displayed.
Use the L[IST] command to verify the new contents of the buffer.

•

Introduction to Oracle9i: SQL C-12

SQL*Plus File Commands
•
•
•
•
•
•
•

SAVE filename
GET filename
START filename
@ filename
EDIT filename
SPOOL filename
EXIT

C-13

Copyright © Oracle Corporation, 2001. All rights reserved.

SQL*Plus File Commands
SQL statements communicate with the Oracle Server. SQL*Plus commands control the environment,
format query results, and manage files. You can use the commands described in the following table:
Command

Description

SAV[E] filename [.ext]
[REP[LACE]APP[END]]

Saves current contents of SQL buffer to a file. Use APPEND
to add to an existing file; use REPLACE to overwrite an
existing file. The default extension is .sql.

GET filename [.ext]
STA[RT] filename [.ext]

Writes the contents of a previously saved file to the SQL
buffer. The default extension for the filename is .sql.
Runs a previously saved command file.

@ filename

Runs a previously saved command file (same as START).

ED[IT]

Invokes the editor and saves the buffer contents to a file
named afiedt.buf.

ED[IT] [filename[.ext]]

Invokes the editor to edit contents of a saved file.

SPO[OL]
[filename[.ext]|
OFF|OUT]

Stores query results in a file. OFF closes the spool file. OUT
closes the spool file and sends the file results to the system
printer.

EXIT

Leaves SQL*Plus.
Introduction to Oracle9i: SQL C-13

Using the SAVE and START Commands

SQL>
1
2*
SQL>

L
SELECT last_name, manager_id, department_id
FROM
employees
SAVE my_query

Created file my_query
SQL> START my_query
LAST_NAME
MANAGER_ID DEPARTMENT_ID
------------------------- ---------- ------------King
90
Kochhar
100
90
...
20 rows selected.

C-14

Copyright © Oracle Corporation, 2001. All rights reserved.

SAVE
Use the SAVE command to store the current contents of the buffer in a file. In this way, you can store
frequently used scripts for use in the future.
START
Use the START command to run a script in SQL*Plus.
EDIT
Use the EDIT command to edit an existing script. This opens an editor with the script file in it. When you
have made the changes, exit the editor to return to the SQL*Plus command line.

Introduction to Oracle9i: SQL C-14

Summary

Use SQL*Plus as an environment to:

•
•
•
•

C-15

Execute SQL statements
Edit SQL statements
Format output
Interact with script files

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
SQL*Plus is an execution environment that you can use to send SQL commands to the database server and
to edit and save SQL commands. You can execute commands from the SQL prompt or from a script file.

Introduction to Oracle9i: SQL C-15

Introduction to Oracle9i: SQL C-16

Writing Advanced Scripts

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this appendix, you should be able
to do the following:

•
•
•

Describe the types of problems that are solved by
using SQL to generate SQL
Write a script that generates a script of DROP
TABLE statements
Write a script that generates a script of INSERT
INTO statements

D-2

Copyright © Oracle Corporation, 2001. All rights reserved.

Lesson Aim
In this appendix, you learn how to write a SQL script to generates a SQL script.

Introduction to Oracle9i: SQL D-2

Using SQL to Generate SQL
SQL

Data
dictionary

SQL script

• SQL can be used to generate scripts in SQL
• The data dictionary
– Is a collection of tables and views that contain database
information
– Is created and maintained by the Oracle server
D-3

Copyright © Oracle Corporation, 2001. All rights reserved.

Using SQL to Generate SQL
SQL can be a powerful tool to generate other SQL statements. In most cases this involves writing a
script file. You can use SQL from SQL to:
• Avoid repetitive coding
• Access information from the data dictionary
• Drop or re-create database objects
• Generate dynamic predicates that contain run-time parameters
The examples used in this lesson involve selecting information from the data dictionary. The data
dictionary is a collection of tables and views that contain information about the database. This
collection is created and maintained by the Oracle Server. All data dictionary tables are owned by
the SYS user. Information stored in the data dictionary includes names of the Oracle Server users,
privileges granted to users, database object names, table constraints, and audition information. There
are four categories of data dictionary views. Each category has a distinct prefix that reflects its
intended use.
Prefix
Description
USER_

Contains details of objects owned by the user

ALL_

Contains details of objects to which the user has been granted access rights, in
addition to objects owned by the user
Contains details of users with DBA privileges to access any object in the database

DBA_
V$_

Stored information about database server performance and locking; available only to
the DBA

Introduction to Oracle9i: SQL D-3

Creating a Basic Script
SELECT 'CREATE TABLE ' || table_name || '_test '
|| 'AS SELECT * FROM ' || table_name
||' WHERE 1=2;'
AS "Create Table Script"
FROM
user_tables;

D-4

Copyright © Oracle Corporation, 2001. All rights reserved.

A Basic Script
The example in the slide produces a report with CREATE TABLE statements from every table you
own. Each CREATE TABLE statement produced in the report includes the syntax to create a table
using the table name with a suffix of _test and having only the structure of the corresponding
existing table. The old table name is obtained from the TABLE_NAME column of the data dictionary
view USER_TABLES.
The next step is to enhance the report to automate the process.
Note: You can query the data dictionary tables to view various database objects that you own. The
data dictionary views frequently used include:
• USER_TABLES: Displays description of the user’s own tables
• USER_OBJECTS: Displays all the objects owned by the user
• USER_TAB_PRIVS_MADE: Displays all grants on objects owned by the user
• USER_COL_PRIVS_MADE: Displays all grants on columns of objects owned by the user

Introduction to Oracle9i: SQL D-4

Controlling the Environment
SET ECHO OFF
SET FEEDBACK OFF
SET PAGESIZE 0

Set system variables
to appropriate values.

SPOOL dropem.sql
SQL STATEMENT
SPOOL OFF

SET FEEDBACK ON
SET PAGESIZE 24
SET ECHO ON

D-5

Set system variables
back to the default
value.

Copyright © Oracle Corporation, 2001. All rights reserved.

Controlling the Environment
In order to execute the SQL statements that are generated, you must capture them in a spool file that
can then be run. You must also plan to clean up the output that is generated and make sure that you
suppress elements such as headings, feedback messages, top titles, and so on. You can accomplish
all of this by using iSQL*Plus commands.

Introduction to Oracle9i: SQL D-5

The Complete Picture
SET ECHO OFF
SET FEEDBACK OFF
SET PAGESIZE 0
SELECT 'DROP TABLE ' || object_name || ';'
FROM
user_objects
WHERE
object_type = 'TABLE'
/
SET FEEDBACK ON
SET PAGESIZE 24
SET ECHO ON

D-6

Copyright © Oracle Corporation, 2001. All rights reserved.

The Complete Picture
The output of the command on the slide is saved into a file called dropem.sql using the Save
Output option in iSQL*Plus. This file contains the following data. This file can now be started from
the iSQL*Plus by locating the script file, loading it, and executing it.

Note: By default, files are spooled into the ORACLE_HOME\ORANT\BIN folder in Windows NT.

Introduction to Oracle9i: SQL D-6

Dumping the Contents of a Table to a File
SET HEADING OFF ECHO OFF FEEDBACK OFF
SET PAGESIZE 0

SELECT
'INSERT INTO departments_test VALUES
(' || department_id || ', ''' || department_name ||
''', ''' || location_id || ''');'
AS "Insert Statements Script"
FROM
departments
/

SET PAGESIZE 24
SET HEADING ON ECHO ON FEEDBACK ON

D-7

Copyright © Oracle Corporation, 2001. All rights reserved.

Dumping Table Contents to a File
Sometimes it is useful to have the values for the rows of a table in a text file in the format of an
INSERT INTO VALUES statement. This script can be run to populate the table, in case the table
has been dropped accidentally.
The example in the slide produces INSERT statements for the DEPARTMENTS_TEST table,
captured in the data.sql file using the Save Output option in iSQL*Plus.
The contents of the data.sql script file are as follows:
INSERT INTO departments_test VALUES
(10, 'Administration', 1700);
INSERT INTO departments_test VALUES
(20, 'Marketing', 1800);
INSERT INTO departments_test VALUES
(50, 'Shipping', 1500);
INSERT INTO departments_test VALUES
(60, 'IT', 1400);
...

Introduction to Oracle9i: SQL D-7

Dumping the Contents of a Table to a File

Source

Result

'''X'''

'X'

''''

'

''''||department_name||''''

'Administration'

''', '''

','

''');'

');

D-8

Copyright © Oracle Corporation, 2001. All rights reserved.

Dumping Table Contents to a File (continued)
You may have noticed the large number of single quotes in the slide on the previous page. A set of
four single quotes produces one single quote in the final statement. Also remember that character and
date values must be surrounded by quotes.
Within a string, to display one single quote, you need to prefix it with another single quote. For
example, in the fifth example in the slide, the surrounding quotes are for the entire string. The second
quote acts as a prefix to display the third quote. Thus the result is one single quote followed by the
parenthesis followed by the semicolon.

Introduction to Oracle9i: SQL D-8

Generating a Dynamic Predicate

COLUMN my_col NEW_VALUE dyn_where_clause
SELECT DECODE('&&deptno', null,
DECODE ('&&hiredate', null, ' ',
'WHERE hire_date=TO_DATE('''||'&&hiredate'',''DD-MON-YYYY'')'),
DECODE ('&&hiredate', null,
'WHERE department_id = ' || '&&deptno',
'WHERE department_id = ' || '&&deptno' ||
' AND hire_date = TO_DATE('''||'&&hiredate'',''DD-MON-YYYY'')'))
AS my_col FROM dual;
SELECT last_name FROM employees &dyn_where_clause;

D-9

Copyright © Oracle Corporation, 2001. All rights reserved.

Generating a Dynamic Predicate
The example in the slide generates a SELECT statement that retrieves data of all employees in a
department who were hired on a specific day. The script generates the WHERE clause dynamically.
Note: Once the user variable is in place, you need to use the UNDEFINE command to delete it.
The first SELECT statement prompts you to enter the department number. If you do not enter any
department number, the department number is treated as null by the DECODE function, and the user
is then prompted for the hire date. If you do not enter any hire date, the hire date is treated as null by
the DECODE function and the dynamic WHERE clause that is generated is also a null, which causes
the second SELECT statement to retrieve all rows from the EMPLOYEES table.
Note: The NEW_V[ALUE]variable specifies a variable to hold a column value. You can reference
the variable in TTITLE commands. Use NEW_VALUE to display column values or the date in the top
title. You must include the column in a BREAK command with the SKIP PAGE action. The
variable name cannot contain a pound sign (#). NEW_VALUE is useful for master/detail reports in
which there is a new master record for each page.

Introduction to Oracle9i: SQL D-9

Generating a Dynamic Predicate (continued)
Note: Here, the hire date must be entered in DD-MON-YYYY format.
The SELECT statement in the previous slide can be interpreted as follows:
IF (<> is not entered) THEN
IF (<> is not entered) THEN
return empty string
ELSE
return the string ‘WHERE hire_date = TO_DATE('<>', 'DD-MON-YYYY')’
ELSE
IF (<> is not entered) THEN
return the string ‘WHERE department_id = <> entered'
ELSE
return the string ‘WHERE deparment_id = <> entered
AND hire_date = TO_DATE(' <>', 'DD-MON-YYYY')’
END IF
The returned string becomes the value of the variable DYN_WHERE_CLAUSE, that will be used in
the second SELECT statement.

Introduction to Oracle9i: SQL D-10

Summary

In this appendix, you should have learned the
following:

•

You can write a SQL script to generate another
SQL script.

•
•

Script files often use the data dictionary.

D-11

You can capture the output in a file.

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
SQL can be used to generate SQL scripts. These scripts can be used to avoid repetitive coding,
drop or re-create objects, get help from the data dictionary, and generate dynamic predicates that
contain run-time parameters.
iSQL*Plus commands can be used to capture the reports generated by the SQL statements and
clean up the output that is generated, such as suppressing headings, feedback messages, and so on.

Introduction to Oracle9i: SQL D-11

Practice D Overview

This practice covers the following topics:

•

Writing a script to describe and select the data
from your tables

•

Writing a script to revoke user privileges

D-12

Copyright © Oracle Corporation, 2001. All rights reserved.

Practice D Overview
In this practice, you gain practical experience in writing SQL to generate SQL.

Introduction to Oracle9i: SQL D-12

Practice D
1. Write a script to describe and select the data from your tables. Use CHR(10) in the select list
with the concatenation operator ( || ) to generate a line feed in your report Save the output of
the script into my_file1.sql. To save the file, select SAVE option for the output and
execute the code. Remember to save the file with a .sql extension. To execute the
my_file1.sql, browse to locate the script, load the script, and execute the script.
2. Use SQL to generate SQL statements that revoke user privileges. Use the data dictionary
views USER_TAB_PRIVS_MADE and USER_COL_PRIVS_MADE.
a. Execute the script \Lab\privs.sql to grant privileges to the user SYSTEM.
b. Query the data dictionary views to check the privileges. In the sample output shown, note
that the data in the GRANTOR column can vary depending on who the GRANTOR is. Also the
last column that has been truncated is the GRANTABLE column.

Introduction to Oracle9i: SQL D-13

Practice D (continued)
c. Produce a script to revoke the privileges. Save the output of the script into my_file2.sql. To
save the file, select the SAVE option for the output, and execute the code. Remember to save the
file with a .sql extension. To execute the my_file2.sql, browse to locate the script, load
the script, and execute the script.

Introduction to Oracle9i: SQL D-14

Oracle Architectural
Components

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives

After completing this appendix, you should be able
to do the following:

E-2

•

Describe the Oracle Server architecture and its
main components

•

List the structures involved in connecting a user
to an Oracle instance

•

List the stages in processing:
–

Queries

–

DML statements

–

Commits

Copyright © Oracle Corporation, 2001. All rights reserved.

Objectives
This appendix introduces Oracle Server architecture by describing the files, processes, and memory structures
involved in establishing a database connection and executing a SQL command.

Introduction to Oracle9i: SQL E-2

Overview
User
process

Instance
SGA
Data buffer
cache

Server
process
PGA

Shared pool
Library
cache
Data dict.
cache

Redo log
buffer

SMON DBW0 PMON CKPT

Parameter
file

Data
files

Control
files

LGWR Others

Redo
log files
Archived
log files

Password
file

E-3

Database

Copyright © Oracle Corporation, 2001. All rights reserved.

Overview
The Oracle Server is an object relational database management system that provides an open, comprehensive,
integrated approach to information management.
Primary Components
There are several processes, memory structures, and files in an Oracle Server; however, not all of them are used
when processing a SQL statement. Some are used to improve the performance of the database, ensure that the
database can be recovered in the event of a software or hardware error, or perform other tasks necessary to maintain
the database. The Oracle Server consists of an Oracle instance and an Oracle database.
Oracle Instance
An Oracle instance is the combination of the background processes and memory structures. The instance must be
started to access the data in the database. Every time an instance is started, a system global area (SGA) is allocated
and Oracle background processes are started.The SGA is a memory area used to store database information that is
shared by database processes.

Introduction to Oracle9i: SQL E-3

Primary Components (continued)
Oracle Instance (continued)
Background processes perform functions on behalf of the invoking process. They consolidate functions that
would otherwise be handled by multiple Oracle programs running for each user. The background processes
perform I/O and monitor other Oracle processes to provide increased parallelism for better performance and
reliability.
Other Processes
The user process is the application program that originates SQL statements. The server process executes the SQL
statements sent from the user process.
Database Files
Database files are operating system files that provide the actual physical storage for database information. The
database files are used to ensure that the data is kept consistent and can be recovered in the event of a failure of
the instance.
Other Files
Nondatabase files are used to configure the instance, authenticate privileged users, and recover the database in
the event of a disk failure.
SQL Statement Processing
The user and server processes are the primary processes involved when a SQL statement is executed; however,
other processes may help the server complete the processing of the SQL statement.
Oracle Database Administrators
Database administrators are responsible for maintaining the Oracle Server so that the server can process user
requests. An understanding of the Oracle architecture is necessary to maintain it effectively.

Introduction to Oracle9i: SQL E-4

Oracle Database Files

Parameter
file
Password
file

E-5

Data
files

Control
files

Redo
log files
Archived
log files

Database

Copyright © Oracle Corporation, 2001. All rights reserved.

Oracle Database Files
An Oracle database is a collection of data that is treated as a unit. The general purpose of a database is to store and
retrieve related information. The database has a logical structure and a physical structure. The physical structure of
the database is the set of operating system files in the database. An Oracle database consists of three file types:
Data files contain the actual data in the database. The data is stored in user-defined tables, but data files also contain
the data dictionary, before-images of modified data, indexes, and other types of structures. A database has at least
one data file. The characteristics of data files are:
•

A data file can be associated with only one database. Data files can have certain characteristics set so they
can automatically extend when the database runs out of space. One or more data files form a logical unit of
database storage called a tablespace. Redo logs contain a record of changes made to the database to enable
recovery of the data in case of failures. A database requires at least two redo log files.

•

Control files contain information necessary to maintain and verify database integrity. For example, a control
file is used to identify the data files and redo log files. A database needs at least one control file.

Introduction to Oracle9i: SQL E-5

Other Key Physical Structures

Parameter
file
Password
file

E-6

Archived
log files
Database

Archived
log files

Copyright © Oracle Corporation, 2001. All rights reserved.

Other Key Files
The Oracle Server also uses other files that are not part of the database:
•

The parameter file defines the characteristics of an Oracle instance. For example, it contains parameters that
size some of the memory structures in the SGA.

•

The password file authenticates which users are permitted to start up and shut down an Oracle instance.

•

Archived redo log files are offline copies of the redo log files that may be necessary to recover from media
failures.

Introduction to Oracle9i: SQL E-6

Oracle Instance

An Oracle instance:

•
•

Is a means to access an Oracle database
Always opens one and only one database

Instance
SGA
Data buffer
cache

Shared pool
Redo log
buffer

SMON DBW0 PMON CKPT

LGWR Others

Memory
structures

Background
processes

Copyright © Oracle Corporation, 2001. All rights reserved.

E-7

Oracle Instance
An Oracle instance consists of the SGA memory structure and the background processes used to manage a
database. An instance is identified by using methods specific to each operating system. The instance can open
and use only one database at a time.
System Global Area
The SGA is a memory area used to store database information that is shared by database processes. It contains
data and control information for the Oracle Server. It is allocated in the virtual memory of the computer where
the Oracle server resides. The SGA consists of several memory structures:
•

The shared pool is used to store the most recently executed SQL statements and the most recently used
data from the data dictionary. These SQL statements may be submitted by a user process or, in the case of
stored procedures, read from the data dictionary.

•

The database buffer cache is used to store the most recently used data. The data is read from, and written
to, the data files.

•

The redo log buffer is used to track changes made to the database by the server and background processes.

Introduction to Oracle9i: SQL E-7

System Global Area (continued)
The purpose of these structures is discussed in detail in later sections of this lesson.
There are also two optional memory structures in the SGA:
•

Java pool: Used to store Java code

•

Large pool: Used to store large memory structures not directly related to SQL statement processing;
for example, data blocks copied during backup and restore operations

Background Processes
The background processes in an instance perform common functions that are needed to service requests from
concurrent users without compromising the integrity and performance of the system. They consolidate
functions that would otherwise be handled by multiple Oracle programs running for each user. The
background processes perform I/O and monitor other Oracle processes to provide increased parallelism for
better performance and reliability.
Depending on its configuration, an Oracle instance may include several background processes, but every
instance includes these five required background processes:
•

Database Writer (DBW0) is responsible for writing changed data from the database buffer cache to
the data files.

•

Log Writer (LGWR) writes changes registered in the redo log buffer to the redo log files.

•

System Monitor (SMON) checks for consistency of the database and, if necessary, initiates recovery
of the database when the database is opened.

•

Process Monitor (PMON) cleans up resources if one of the Oracle processes fails.

•

The Checkpoint Process (CKPT) is responsible for updating database status information in the control
files and data files whenever changes in the buffer cache are permanently recorded in the database.

The following sections of this lesson explain how a server process uses some of the components of the
Oracle instance and database to process SQL statements submitted by a user process.

Introduction to Oracle9i: SQL E-8

Processing a SQL Statement
•

Connect to an instance using:
– The user process
– The server process

•

The Oracle Server components that are used
depend on the type of SQL statement:
– Queries return rows
– DML statements log changes
– Commit ensures transaction recovery

•

E-9

Some Oracle Server components do not
participate in SQL statement processing.

Copyright © Oracle Corporation, 2001. All rights reserved.

Components Used to Process SQL
Not all of the components of an Oracle instance are used to process SQL statements.The user and server
processes are used to connect a user to an Oracle instance. These processes are not part of the Oracle instance, but
are required to process a SQL statement.
Some of the background processes, SGA structures, and database files are used to process SQL statements.
Depending on the type of SQL statement, different components are used:
•

Queries require additional processing to return rows to the user.

•

Data manipulation language (DML) statements require additional processing to log the changes
made to the data.

•

Commit processing ensures that the modified data in a transaction can be recovered.

Some required background processes do not directly participate in processing a SQL statement but are used to
improve performance and to recover the database.
The optional background process, ARC0, is used to ensure that a production database can be recovered.

Introduction to Oracle9i: SQL E-9

Connecting to an Instance
User

Server
Oracle server

User

Server

Client
Application server
User

Server
Server

Browser

E-10

Copyright © Oracle Corporation, 2001. All rights reserved.

Processes Used to Connect to an Instance
Before users can submit SQL statements to the Oracle Server, they must connect to an instance.
The user starts a tool such as iSQL*Plus or runs an application developed using a tool such as Oracle Forms. This
application or tool is executed in a user process.
In the most basic configuration, when a user logs on to the Oracle Server, a process is created on the computer
running the Oracle server. This process is called a server process. The server process communicates with the
Oracle instance on behalf of the user process that runs on the client. The server process executes SQL statements
on behalf of the user.
Connection
A connection is a communication pathway between a user process and an Oracle Server. A database user can
connect to an Oracle Server in one of three ways:
•

The user logs on to the operating system running the Oracle instance and starts an application or tool that
accesses the database on that system. The communication pathway is established using the interprocess
communication mechanisms available on the host operating system.

Introduction to Oracle9i: SQL E-10

Connection (continued)
•

The user starts the application or tool on a local computer and connects over a network to the computer
running the Oracle instance. In this configuration, called client-server, network software is used to
communicate between the user and the Oracle Server.

•

In a three-tiered connection, the user’s computer communicates over the network to an application or a
network server, which is connected through a network to the machine running the Oracle instance. For
example, the user runs a browser on a network computer to use an application residing on an NT server
that retrieves data from an Oracle database running on a UNIX host.

Sessions
A session is a specific connection of a user to an Oracle Server. The session starts when the user is validated by
the Oracle Server, and it ends when the user logs out or when there is an abnormal termination. For a given
database user, many concurrent sessions are possible if the user logs on from many tools, applications, or
terminals at the same time. Except for some specialized database administration tools, starting a database
session requires that the Oracle Server be available for use.
Note: The type of connection explained here, where there is a one-to-one correspondence between a user and
server process, is called a dedicated server connection.

Introduction to Oracle9i: SQL E-11

Processing a Query

•

Parse:
– Search for identical statement
– Check syntax, object names, and privileges
– Lock objects used during parse
– Create and store execution plan

•
•

Execute: Identify rows selected
Fetch: Return rows to user process

Copyright © Oracle Corporation, 2001. All rights reserved.

E-12

Query Processing Steps
Queries are different from other types of SQL statements because, if successful, they return data as results.
Whereas other statements simply return success or failure, a query can return one row or thousands of rows.
There are three main stages in the processing of a query:
•

Parse

•

Execute

•

Fetch

Parsing a SQL Statement
During the parse stage, the SQL statement is passed from the user process to the server process, and a parsed
representation of the SQL statement is loaded into a shared SQL area.
During the parse, the server process performs the following functions:
•

Searches for an existing copy of the SQL statement in the shared pool

•

Validates the SQL statement by checking its syntax

•

Performs data dictionary lookups to validate table and column definitions

Introduction to Oracle9i: SQL E-12

The Shared Pool
Shared pool
Library
cache
Data dictionary
cache

•

The library cache contains the SQL statement text,
parsed code, and execution plan.

•

The data dictionary cache contains table, column,
and other object definitions and privileges.
The shared pool is sized by SHARED_POOL_SIZE.

•
E-13

Copyright © Oracle Corporation, 2001. All rights reserved.

Shared Pool Components
During the parse stage, the server process uses the area in the SGA known as the shared pool to compile the SQL
statement. The shared pool has two primary components:
•

Library cache

•

Data dictionary cache

Library Cache
The library cache stores information about the most recently used SQL statements in a memory structure called a
shared SQL area. The shared SQL area contains:
•

The text of the SQL statement

•

The parse tree: A compiled version of the statement

•

The execution plan: The steps to be taken when executing the statement

The optimizer is the function in the Oracle Server that determines the optimal execution plan.

Introduction to Oracle9i: SQL E-13

Shared Pool Components (continued)
Library Cache (continued)
If a SQL statement is reexecuted and a shared SQL area already contains the execution plan for the
statement, the server process does not need to parse the statement. The library cache improves the
performance of applications that reuse SQL statements by reducing parse time and memory requirements. If
the SQL statement is not reused, it is eventually aged out of the library cache.
Data Dictionary Cache
The data dictionary cache, also known as the dictionary cache or row cache, is a collection of the most
recently used definitions in the database. It includes information about database files, tables, indexes,
columns, users, privileges, and other database objects.
During the parse phase, the server process looks for the information in the dictionary cache to resolve the
object names specified in the SQL statement and to validate the access privileges. If necessary, the server
process initiates the loading of this information from the data files.
Sizing the Shared Pool
The size of the shared pool is specified by the initialization parameter SHARED_POOL_SIZE.

Introduction to Oracle9i: SQL E-14

Database Buffer Cache

Data buffer
cache

•
•
•

E-15

Stores the most recently used blocks
Size of a buffer based on DB_BLOCK_SIZE
Number of buffers defined by DB_BLOCK_BUFFERS

Copyright © Oracle Corporation, 2001. All rights reserved.

Function of the Database Buffer Cache
When a query is processed, the server process looks in the database buffer cache for any blocks it needs. If the
block is not found in the database buffer cache, the server process reads the block from the data file and places a
copy in the buffer cache. Because subsequent requests for the same block may find the block in memory, the
requests may not require physical reads. The Oracle Server uses a least recently used algorithm to age out buffers
that have not been accessed recently to make room for new blocks in the buffer cache.
Sizing the Database Buffer Cache
The size of each buffer in the buffer cache is equal to the size of an Oracle block, and it is specified by the
DB_BLOCK_SIZE parameter. The number of buffers is equal to the value of the DB_BLOCK_BUFFERS
parameter.

Introduction to Oracle9i: SQL E-15

Program Global Area (PGA)
•
•
•

Not shared
Writable only by the server process
Contains:
– Sort area
– Session information
– Cursor state
– Stack space

Server
process
PGA

E-16

Copyright © Oracle Corporation, 2001. All rights reserved.

Program Global Area Components
A program global area (PGA) is a memory region that contains data and control information for a server process. It
is a nonshared memory created by Oracle when a server process is started. Access to it is exclusive to that server
process and is read and written only by the Oracle Server code acting on behalf of it. The PGA memory allocated by
each server process attached to an Oracle instance is referred to as the aggregated PGA memory allocated by the
instance.
In a dedicated server configuration, the PGA of the server includes these components:
•

Sort area: Used for any sorts that may be required to process the SQL statement

•

Session information: Includes user privileges and performance statistics for the session

•

Cursor state: Indicates the stage in the processing of the SQL statements that are currently used by the
session

•

Stack space: Contains other session variables

The PGA is allocated when a process is created and deallocated when the process is terminated.

Introduction to Oracle9i: SQL E-16

Processing a DML Statement
SGA

User
process

Shared pool

Data buffer
cache

Redo log
buffer

UPDATE emp ...

4
Server
process

1

2

3
Data
files

Control Redo
files log files

1
Database

E-17

Copyright © Oracle Corporation, 2001. All rights reserved.

DML Processing Steps
A data manipulation language (DML) statement requires only two phases of processing:
•

Parse is the same as the parse phase used for processing a query

•

Execute requires additional processing to make data changes

DML Execute Phase
To execute a DML statement:
•

If the data and rollback blocks are not already in the buffer cache, the server process reads them from the
data files into the buffer cache.

•

The server process places locks on the rows that are to be modified.

•

In the redo log buffer, the server process records the changes to be made to the rollback and data.

•

The rollback block changes record the values of the data before it is modified. The rollback block is used to
store the before image of the data, so that the DML statements can be rolled back if necessary.

•

The data blocks changes record the new values of the data.

Introduction to Oracle9i: SQL E-17

DML Processing Steps (continued)
DML Execute Phase (continued)
The server process records the before image to the rollback block and updates the data block. Both of
these changes are done in the database buffer cache. Any changed blocks in the buffer cache are
marked as dirty buffers: that is, buffers that are not the same as the corresponding blocks on the disk.
The processing of a DELETE or INSERT command uses similar steps. The before image for a
DELETE contains the column values in the deleted row, and the before image of an INSERT contains
the row location information.
Because the changes made to the blocks are only recorded in memory structures and are not written
immediately to disk, a computer failure that causes the loss of the SGA can also lose these changes.

Introduction to Oracle9i: SQL E-18

Redo Log Buffer

Redo log
buffer

•
•
•
•

E-19

Has its size defined by LOG_BUFFER
Records changes made through the instance
Is used sequentially
Is a circular buffer

Copyright © Oracle Corporation, 2001. All rights reserved.

Redo Log Buffer Characteristics
The server process records most of the changes made to data file blocks in the redo log buffer, which is a part of
the SGA. The redo log buffer has the following characteristics:
• Its size in bytes is defined by the LOG_BUFFER parameter.
•

It records the block that is changed, the location of the change, and the new value in a redo entry. A redo
entry makes no distinction between the type of block that is changed; it simply records which bytes are
changed in the block.

•

The redo log buffer is used sequentially, and changes made by one transaction may be interleaved with
changes made by other transactions.

•

It is a circular buffer that is reused after it is filled, but only after all the old redo entries are recorded in the
redo log files.

Introduction to Oracle9i: SQL E-19

Rollback Segment
Old image

New
image

Table
Rollback segment

DML statement

E-20

Copyright © Oracle Corporation, 2001. All rights reserved.

Rollback Segment
Before making a change, the server process saves the old data value into a rollback segment. This before image is
used to:
•

Undo the changes if the transaction is rolled back

•

Provide read consistency by ensuring that other transactions do not see uncommitted changes made by the
DML statement

•

Recover the database to a consistent state in case of failures

Rollback segments, like tables and indexes, exist in data files, and rollback blocks are brought into the database
buffer cache as required. Rollback segments are created by the DBA.
Changes to rollback segments are recorded in the redo log buffer.

Introduction to Oracle9i: SQL E-20

COMMIT Processing
Instance
SGA

1
Server
process

Shared pool

Data buffer Redo log
cache
buffer

4
LGWR

3

2
Data
files

Control Redo
files log files

User
process
Database

E-21

Copyright © Oracle Corporation, 2001. All rights reserved.

Fast COMMIT
The Oracle Server uses a fast commit mechanism that guarantees that the committed changes can be recovered in
case of instance failure.
System Change Number
Whenever a transaction commits, the Oracle Server assigns a commit system change number (SCN) to the
transaction. The SCN is monotonically incremented and is unique within the database. It is used by the Oracle
Server as an internal time stamp to synchronize data and to provide read consistency when data is retrieved from
the data files. Using the SCN enables the Oracle Server to perform consistency checks without depending on the
date and time of the operating system.
Steps in Processing COMMITs
When a COMMIT is issued, the following steps are performed:
•

The server process places a commit record, along with the SCN, in the redo log buffer.

•

LGWR performs a contiguous write of all the redo log buffer entries up to and including
the commit record to the redo log files. After this point, the Oracle Server can guarantee that the changes will
not be lost even if there is an instance failure.

Introduction to Oracle9i: SQL E-21

Steps in Processing COMMITs (continued)
•

The user is informed that the COMMIT is complete.

•

The server process records information to indicate that the transaction is complete and that
resource locks can be released.

Flushing of the dirty buffers to the data file is performed independently by DBW0 and can occur either
before or after the commit.
Advantages of the Fast COMMIT
The fast commit mechanism ensures data recovery by writing changes to the redo log buffer instead of
the data files. It has the following advantages:
•

Sequential writes to the log files are faster than writing to di fferent blocks in the data file.

•

Only the minimal information that is necessary to record changes is written to the log files,
whereas writing to the data files would require whole blocks of data to be written.

•

If multiple transactions request to commit at the same time, the instance piggybacks redo log
records into a single write.

•

Unless the redo log buffer is particularly full, only one synchronous write is required per
transaction. If piggybacking occurs, there can be less than one synchronous write per transaction.

•

Because the redo log buffer may be flushed before the COMMIT, the size of the transaction does
not affect the amount of time needed for an actual COMMIT operation.

Note: Rolling back a transaction does not trigger LGWR to write to disk. The Oracle Server always rolls
back uncommitted changes when recovering from failures. If there is a failure after a rollback, before the
rollback entries are recorded on disk, the absence of a commit record is sufficient to ensure that the
changes made by the transaction are rolled back.

Introduction to Oracle9i: SQL E-22

Log Writer (LGWR)
SGA

Shared pool

• There is a commit

Data buffer Redo log
cache
buffer

• The redo buffer log
is one-third full
LGWR

Data
files

LGWR writes when:

Control Redo
files log files

• There is more than
1 MB of redo
• Before DBW0 writes

Database

E-23

Copyright © Oracle Corporation, 2001. All rights reserved.

LOG Writer
LGWR performs sequential writes from the redo log buffer to the redo log file under the following situations:
•

When a transaction commits

•

When the redo log buffer is one-third full

•

When there is more than a megabyte of changes recorded in the redo log buffer

•

Before DBW0 writes modified blocks in the database buffer cache to the data files

Because the redo is needed for recovery, LGWR confirms the COMMIT only after the redo is written to disk.

Introduction to Oracle9i: SQL E-23

Other Instance Processes
•

Other required processes:
– Database Writer (DBW0)
– Process Monitor (PMON)
– System Monitor (SMON)
– Checkpoint (CKPT)

•

The archive process (ARC0) is usually created
in a production database

E-24

Copyright © Oracle Corporation, 2001. All rights reserved.

Other Required Processes
Four other required processes do not participate directly in processing SQL statements:
•

Database Writer (DBW0)

•

Process Monitor (PMON)

•

System Monitor (SMON)

•

Checkpoint (CKPT)

The checkpoint process is used to synchronize database files.
The Archiver Process
All other background processes are optional, depending on the configuration of the database; however, one of them,
ARC0, is crucial to recovering a database after the loss of a disk. The ARC0 process is usually created in a
production database.

Introduction to Oracle9i: SQL E-24

Database Writer (DBW0)
SGA

Shared pool

DBW0 writes when:
Data buffer Redo log
cache
buffer

•

There are many dirty
buffers

•

There are few free
buffers

•
•

Timeout occurs

DBW0

Data
files

Control Redo
files log files

Checkpoint occurs

Database

E-25

Copyright © Oracle Corporation, 2001. All rights reserved.

Database Writer
The server process records changes to rollback and data blocks in the buffer cache. The Database Writer (DBW0)
writes the dirty buffers from the database buffer cache to the data files. It ensures that a sufficient number of free
buffers (buffers that can be overwritten when server processes need to read in blocks from the data files) are
available in the database buffer cache. Database performance is improved because server processes make changes
only in the buffer cache, and the DBW0 defers writing to the data files until one of the following eve nts occurs:
•

The number of dirty buffers reaches a threshold value

•

A process scans a specified number of blocks when scanning for free buffers and cannot
find any

•

A timeout occurs (every three seconds)

•

A checkpoint occurs (A checkpoint is a means of synchronizing the database buffer cache with the data file.)

Introduction to Oracle9i: SQL E-25

SMON: System Monitor

•

Automatically recovers the instance:
– Rolls forward changes in the redo logs
– Opens the database for user access
– Rolls back uncommitted transactions

•
•

Coalesces free space
Deallocates temporary segments

E-26

Copyright © Oracle Corporation, 2001. All rights reserved.

SMON: System Monitor
If the Oracle instance fails, any information in the SGA that has not been written to disk is lost. For example, the
failure of the operating system causes an instance failure. Afte r the loss of the instance, the background process
SMON automatically performs instance recovery when the database is reopened. Instance recovery consists of the
following steps:
•

Rolling forward to recover data that has not been recorded in the data files but that has been recorded in the
online redo log. This data has not been written to disk because of the loss of the SGA during instance failure.
During this process, SMON reads the redo log files and applies the changes recorded in the redo log to the data
blocks. Because all committed transaction have been written to the redo logs, this process completely
recovers these transactions.

•

Opening the database so users can log on. Any data that is not locked by unrecovered transactions is
immediately available.

•

Rolling back uncommitted transactions. They are rolled back by SMON or by the individual server processes
as they access locked data.

SMON also performs some space maintenance functions:
•

It combines, or coalesces, adjacent areas of free space in the data files.

•

It deallocates temporary segments to return them as free space in data files. Temporary segments are used to
store data during SQL statement processing.
Introduction to Oracle9i: SQL E-26

PMON: Process Monitor

Cleans up after failed processes by:

•
•
•

Rolling back the transaction
Releasing locks
Releasing other resources

E-27

Copyright © Oracle Corporation, 2001. All rights reserved.

PMON Functionality
The background process PMON cleans up after failed processes by:
•

Rolling back the user’s current transaction

•

Releasing all currently held table or row locks

•

Freeing other resources currently reserved by the user

Introduction to Oracle9i: SQL E-27

Summary

In this appendix, you should have learned how to:

E-28

•

Identify database files: data files, control files,
online redo logs

•

Describe SGA memory structures: DB buffer
cache, shared SQL pool, and redo log buffer

•

Explain primary background processes:
DBW0, LGWR, CKPT, PMON, SMON, and ARC0

•

List SQL processing steps: parse, execute, fetch

Copyright © Oracle Corporation, 2001. All rights reserved.

Summary
The Oracle database includes these files:
• Control files: Contain information required to verify the integrity of the database, including the names
of the other files in the database (The control files are usually mirrored.)
• Data files: Contain the data in the database, including tables, indexes, rollback segments, and
temporary segments
• Online redo logs: Contain the changes made to the data files (Online redo logs are used for recovery
and are usually mirrored.)
Other files commonly used with the database include:
• Parameter file: Defines the characteristics of an Oracle instance
• Password file: Authenticates privileged database users
• Archived redo logs: Are backups of the online redo logs

Introduction to Oracle9i: SQL E-28

SGA Memory Structures
The System Global Area (SGA) has three primary structures:
•

Shared pool: Stores the most recently executed SQL statements and the most recently used data
from the data dictionary

•

Database buffer cache: Stores the most recently used data

•

Redo log buffer: Records changes made to the database using the instance

Background Processes
A production Oracle instance includes these processes:
•

Database Writer (DBW0): Writes changed data to the data files

•

Log Writer (LGWR): Records changes to the data files in the online redo log files

•

System Monitor (SMON): Checks for consistency and initiates recovery of the database when the
database is opened

•

Process Monitor (PMON): Cleans up the resources if one of the processes fails

•

Checkpoint Process (CKPT): Updates the database status information after a checkpoint

•

Archiver (ARC0): Backs up the online redo log to ensure recovery after a media failure (This
process is optional, but is usually included in a production instance.)

Depending on its configuration, the instance may also include other processes.
SQL Statement Processing Steps
The steps used to process a SQL statement include:
•

Parse: Compiles the SQL statement

•

Execute: Identifies selected rows or applies DML changes to the data

•

Fetch: Returns the rows queried by a SELECT statement

Introduction to Oracle9i: SQL E-29

Introduction to Oracle9i: SQL E-30

Index
Note: A bolded number or letter refers to an entire lesson or appendix.
A
APPEND Command C-11
ACCESS PARAMETER 20-19
Adding Data through a View 11-16
ADD_MONTHS Function 3-21
ALL Operator 6-16
Alias 1-4, 1-17, 1-16, 2-7, 2-24, 11-9
Table Aliases 4-12
ALL INSERT (Conditional) 20-7
ALL_COL_COMMENT Data Dictionary View 9-30
ALL_TAB_COMMENT Data Dictionary View 9-30
ALTER SEQUENCE Statement 12-12
ALTER TABLE Statement 9-20, 9-21, 10-17, 10-20, 10-21, 13-11
ALTER USER Statement 13-11
Ambiguous Column Names 4-11
American National Standards Institute I-24
ANSI I-24
ANY Operator 6-15
Application Server I-5
Archived Redo Log File E-6
Arguments 3-3, 3-5
Arithmetic Expression 1-9
Arithmetic Operator 1-9
AS Subquery Clause 9-18
Assigning Privileges 13-7
Attributes I-16, I-19
AVG Function 5-6, 5-7

Introduction to Oracle9i: SQL Index-1

Index
B
Background Processes E-3, E-7
BETWEEN Operator 2-10
BREAK Command 7-18
BTITLE Command 7-19
C
CHANGE Command C-12
Caching Sequence 12-1
Calculations in Expressions 1-9
Cardinality I-18
Cartesian Product 4-4, 4-5
CASE Expression 3-51, 3-52, 18-12
CASCADE CONSTRAINTS Clause 10-22
Character Data Type in Functions 3-4
Character Strings 2-5, 2-6
CHECK Constraint 10-16
Checkpoint Process e-8
Child Node 19-10
CLEAR BREAK Command 7-18
COALESCE Function 3-49
COLUMN Command 7-16, 7-17
Column Level Constraints 10-8
Command or Script Files 7-20
COMMENT Statement 9-30
COMMIT Statement 8-2, 8-33, 8-35, 8-39, 8-40, 9-8
Comparison Operator, Comparison Conditions 2-7, 18-4
Composite Column 17-17
Composite Unique Key 10-10
CONCAT Function 3-11
Concatenated Groupings 17-21
Concatenation Operator 1-18
Introduction to Oracle9i: SQL Index-2

Index
C
Conditional FIRST INSERT 20-7, 20-13, 20-14
Conditional If-Then-Else Logic 3-51
Conditional INSERT ALL 20-7, 20-11
Conditional Processing 3-51
Conditions, Logical 2-15
CONNECT BY Clause 19-5, 19-7, 19-13
CONSTRAINTS 10
CASCADE CONSTRAINTS Clause 10-22
CHECK Constraint 10-16
Column-Level Constraints 10-8
Defining Constraints 10-5
Deleting a Record with an Integrity Constraint 8-22
Disabling 10-20
Dropping a Constraint 10-19
FOREIGN KEY 10-13, 10-14, 10-15, I-19
NOT NULL Constraint 10-7
Primary Key 10-11
READ ONLY Constraint 11-19
REFERENCE Constraint 10-15
Referential Integrity Constraint 10-13
Table-Level Constraints 10-8
UNIQUE Constraint 10-9, 10-10
Controlling Database Access 13
Control File e-5
Correlated Subquery 18-2, 18-13, 18-14, 18-15, 18-21, 18-24
Correlated UPDATE 18-22
Correlation 18-17
COUNT Function 5-8
Introduction to Oracle9i: SQL Index-3

C
CREATE DATABASE Statement 16-9
CREATE DIRECTORY Statement 20-20
CREATE INDEX Statement 12-17, 20-24
Creating Scripts 1-26
CREATE SEQUENCE Statement 12-5
CREATE TABLE Statement 9
CREATE USER Statement 13-6
CREATE VIEW Statement 11-7
Cross Tabular Reports 17-9
Cross Tabulation Rows 17-6
Cross Tabulation Values 17-10
CUBE Operator 17-2, 17-6, 17-9
CURRENT_DATE Function 16-6
CURRENT_TIMESTAMP Function 16-7
CURRVAL 9-7, 12-8
CYCLE Clause (Sequences) 12-6
D
Date Functions 3-6
Data Control Language (DCL) Statements 8-33, 9
Data Definition Language (DDL) Statements 8-33, 9-5, 13
Data Manipulation Language (DML) Statements 8
DML Operations through a View 11-14
Data Dictionary Tables 9-9, D-3
Data Dictionary Cache E-13, E-14
Data File E-5
Data from More than One Table (Joins) 4
Data Structures in the Oracle Database 9-3, 9-5

Introduction to Oracle9i: SQL Index-4

Index
D
Data Types 3-25
Data Warehouse Applications I-8
Database Links 13-19
Database Writer E-8
Date Conversion Functions 3-4, 3-35
Datetime Data Type 9-14
Datetime Functions 16-2
Daylight Savings Time 16-5
DBTIMEZONE Function 16-9
DECODE Expression 3-51, 3-54
DEFAULT Clause 8-26, 8-27, 9-7
Default Date Display 2-6, 3-17
DEFAULT DIRECTORY 20-19
Default Sort Order 2-23
DEFINE Command 7-5, 7-11
Defining Constraints 10-5
DELETE Statement 8-19, 8-20, 13-16
DESCRIBE Command 1-29, 8-7, 10-24, 11-13, C-7
DISABLE Clause 10-20
DISTINCT Keyword 1-4, 1-23, 5-5, 5-10
Dropping a Constraint 10-19
DROP ANY INDEX Statement 12-2
DROP ANY VIEW Statement 11-20

Introduction to Oracle9i: SQL Index-5

D
DROP COLUMN Clause 9-25
DROP INDEX Statement 12
DROP SEQUENCE Statement 12-14
DROP SYNONYM 12-24
DROP TABLE Statement

9-27

DROP UNUSED COLUMNS Clause 9-26
DROP VIEW Statement 11-20
DUAL Table 3-14, 3-18
Duplicate Records 15-11
E
E-business 19-6, I-3
EDIT Command C-14
Entity I-16, I-17, I-18
Entity Relationship Diagram I-16, I-17, I-16
Equijoins 4-8, 4-27
ESCAPE Option 2-13
Exclusive Locks 8-46

Introduction to Oracle9i: SQL Index-6

E
Execute Button (in iSQL*Plus) 1-7, 1-32
Executing SQL 1-26
EXISTS Operator 18-18, 18-19
Explicit Data Type Conversion 3-25
Expressions
Calculations in Expressions 1-9
CASE Expression 3-51, 3-52, 18-12
DECODE Expression 3-51, 3-54
If-Then-Else Logic 3-51
External Tables 20
Conditional FIRST INSERT 20-7, 20-13, 20-14
Conditional INSERT ALL 20-7, 20-11
ORGANIZATION EXTERNAL Clause 20-18, 20-19
Pivoting INSERT 20-7, 20-15
Unconditional INSERT 20-7, 20-10
REJECT LIMIT Clause 20-19
TYPE ACCESS_DRIVER_TYPE 20-19
EXTRACT Function 16-10
F
FOREIGN KEY Constraint 10-13, 10-14, 10-15, o-19
Format Mode (fm)

3-31

FRACTIONAL_SECONDS_PRECISION 9-15
FROM Clause 1
FROM Clause Query 11-21, 18-2, 18-10
FROM_TZ Function 16-11

Introduction to Oracle9i: SQL Index-7

Index
F
Functions 3, 5
AVG (Average) 5-6, 5-7
Character Data Type in Functions 3-4
COALESCE Function 3-49
CONCAT Function 3-11
COUNT Function 5-8
CURRENT_DATE Function 16-6
CURRENT_TIMESTAMP Function 16-7
Date Conversion Functions 3-4, 3-35
Datetime Functions 16-2
DBTIMEZONE Function 16-9
EXTRACT Function 16-10
TIMEZONE_ABBR 16-10
TIMEZONE_REGION 16-10
FROM_TZ Function 16-11
INITCAP Function 3-9
INSTR Function 3-11
LAST_DAY Function 3-21
LENGTH Function 3-11
LOCALTIMESTAMP Function 16-8
LOWER Function 3-9
LPAD Function 3-11
MAX Function 5-6, 5-7
MIN Function 5-6, 5-7
MONTHS_BETWEEN Function 3-6, 3-21
Multiple-row Function 3-4

Introduction to Oracle9i: SQL Index-8

F
Functions 3, 5
NEXT_DAY Function 3-21
NULLIF Function 3-48
Number Functions 3-13
NVL Function 3-45, 3-46, 5-5, 5-12
NVL2 Function 3-47
Returning a Value 3-3
ROUND Function 3-14, 3-21, 3-23
SESSIONTIMEZONE Function 16-9
STDDEV Function 5-7
SUBSTR Function 3-11
SUM Function 5-6, 5-7
SYS Function 9-9
SYSDATE Function 3-18, 3-20, 9-7
TO_CHAR Function 3-31, 3-37, 3-39
TO_DATE Function 3-39
TO_NUMBER Function 3-39
TO_TIMESTAMP Function 16-12
TO_YMINTERVAL Function 16-13
TRIM Function 3-11
TRUNC Function 3-15, 3-21, 3-23
TZOFFSET 16-14 Function
UPPER Function 3-9, 3-10
USER Function 9-7
Function-based Indexes 12-21

Introduction to Oracle9i: SQL Index-9

G
Generating Unique Numbers 12-3
GRANT Statement 13
Greenwich Mean Time 16-3
Gregorian Calendar 16-10
GROUP BY Clause 5-13, 5-14, 5-15, 5-16, 17-3, 17-4
GROUP BY ROLLUP 17-17
Grouping Data 5, 17-2
Group Functions 5
Group Functions in a Subquery 6-10
Group Functions and NULL Values 5-11
GROUPING SETS Clause 17-12, 17-11, 17-13
Guidelines for Creating a View 11-8
H
Hash Sign 3-38
HAVING Clause 5-21, 5-22, 5-23, 6-11, 17-5
Hierarchical Queries 19
Child Node 19-10
CONNECT BY Clause 19-5, 19-7, 19-13
PRIOR Clause 19-7
Pruning the Tree 19-13
START WITH Clause 19-5, 19-6
I
If-Then-Else Logic 3-51
Implicit Data Type Conversion 3-25
Indexes 9-3, 12
CREATE INDEX Statement 12-17, 20-24
Naming Indexes 20-2
Non-unique Indexes 12-16
Unique Index 10-10, 12-6
When to Create an Index 12-18
Introduction to Oracle9i: SQL Index-10

Index
I
INITCAP Function 3-9
Inline Views 11-2, 11-21
Inner Query 6-3, 6-4, 6-5, 18-5
INSERT Statement 8-5, 8-6, 8-11, 13-18, 20-2, 20-7
Conditional FIRST INSERT 20-7, 20-13, 20-14
Conditional INSERT ALL 20-7, 20-11
Pivoting INSERT 20-7, 20-15
Unconditional INSERT 20-7, 20-10
VALUES Clause 8-5
INSTR Function 3-11
Integrity Constraints 8-17, 10-2
International Standards Organization (ISO) I-24
Internet Features I-7
INTERSECT Operator 15-12
INTERVAL YEAR TO

MONTH Data Type 9-17

IS NOT NULL Operator 2-14
IS NULL Operator 2-14
iSLQL*Plus 1-24
J
Java I-23
Joining Tables 1-3, 4
Cartesian Product 4-4, 4-5
Equijoins 4-8, 4-27
Joining a Table to Itself 4-19
Joining More than Two Tables 4-13
Joining When there is No Matching Record 4-34

Introduction to Oracle9i: SQL Index-11

J
Joining Tables 1-3, 4
Left Table 4-32
Natural Joins 4-24, 4-26
Nonequijoins 4-14, 4-15
ON Clause 4-28, 4-29
Outer Join 4-17, 4-18
RIGHT Table 4-33
Three-Way Join 4-30
K
Keywords 1-4, 1-7
L
LAST_DAY Function 3-21
LENGTH Function 3-11
LEVEL Psuedocolumn 19-10
Library Cache e-13
LIKE Operator 2-12
LIST Command c-11
Literal Values 1-20
Loading Scripts 1-32
LOCALTIMESTAMP Function 16-8
Locks 8-45
Exclusive Locks 8-46
Logical Conditions 2-15
Logical Subsets 11-4
LogWriter (LGWR) E-6, E-8
LOWER Function 3-9
LPAD Function 3-11

Introduction to Oracle9i: SQL Index-12

M
MAX Function 5-6, 5-7
MERGE Statement 8-28, 8-29
WHEN NOT MATCHED Clause 8-31
MIN Function 5-6, 5-7
MINUS Operator 15-14
MODIFY Clause 9-24
Modify Column 9-23
MONTHS_BETWEEN Function 3-6, 3-21
Multiple Column Subquery 6-7, 18-2, 18-8
Multiple-row Function 3-4
Multiple-row Subquery 6-2, 6-7, 6-14, 18-6
Multitable Inserts 20-2, 20-5, 20-7
N
Naming Conventions for Tables 9-4
Naming Indexes 20-2
Natural Joins 4-24, 4-26
Nested Queries 6-4, 18-4
Nested Functions 3-42
NEXT_DAY Function 3-21
NEXTVAL Psuedocolumn 9-7, 12-8
Nonequijoins 4-14, 4-15
Nonpairwise Comparisons 18-7
Non-unique Indexes 12-16
NOT EXISTS Operator 18-20
NOT IN Operator 18-20
NOT NULL Constraint 10-7
NULL

1-14, 1-15, 2-14, o-19

NULLIF Function 3-48
Number Functions 3-13
NVL Function 3-45, 3-46, 5-5, 5-12
NVL2 Function 3-47
Introduction to Oracle9i: SQL Index-13

O
Object Privileges 13-2
Object Relational Database Management System (ORDBMS) I-2, I-7, I-12
Object-oriented Programming I-7
ON Clause 4-28, 4-29
ON DELETE CASCADE Clause 10-15
ON DELETE SET NULL Clause 10-15
On Line Transaction Processing I-8
OR REPLACE Clause 11-12
Oracle Instance E-3, E-7, I-23
Oracle9i Application Server I-4
Oracle9i Database I-4
ORDER BY Clause 2, 15-20
Default Sort Order 2-23
Order of Precedence 1-12
ORGANIZATION EXTERNAL Clause 20-18, 20-19
Outer Join 4-17, 4-18
Outer Query 6-5, 18-5
P
Pairwize Comparisions 18-7
Paremeter File E-6
Parent-child Relationship 19-4
Password File E-6
Pivoting INSERT 20-7, 20-15
Primary Key 10-11
PRIOR Clause 19-7
Privileges 13
Object Privileges 13-2
Process Monitor E-8
Program Global Area E-16
Projection 1-3
PUBLIC Keyword 13-5
Introduction to Oracle9i: SQL Index-14

R
Read Consistency 8-43, 8-44
READ ONLY Constraint 11-19
REM Command 7-21
REFERENCE Constraint 10-13, 10-15
Referential Integrity Constraint 10-13
REJECT LIMIT Clause 20-19
Relational Database Management System (RDBMS) I-2, I-13, I-14
Relationships I-16
RENAME Command 9-28
Restricting Rows 2-2
Retrieving Data from a View 11-10
Returning a Value 3-3
REVOKE Command 13-17
ROLLBACK Statement 8-2, 8-33, 8-35, 8-38, 8-41, E-20
Rollback Segment e-20
ROLLUP Clause 17-2, 17-6, 17-7, 17-8
Root Node 19-10
ROUND Function 3-14, 3-21, 3-23
Row I-19, 17-8
ROWNUMBER Psuedocolumn
RR Date Format 3-41
Rules of Precedence 1-13, 2-19

Introduction to Oracle9i: SQL Index-15

Index
S
SAVE Command C-14
SAVEPOINT Statement 8-2, 8-35, 8-36
Scalar Subquery 18-11
Schema 9-6, 13-4
Script or Command Files 7-20, 7-22, C-2
Creating Scripts 1-26
Loading Scripts 1-32
Search 2-12
SELECT Statement 1
Selection 1-3
Sequences 9-13, 12
Caching Sequence Values 12-11
CREATE SEQUENCE Statement 12-5
CURRVAL

9-7, 12-8

CYCLE Clause 12-6
Generating Unique Numbers 12-3
NEXTVAL

9-7, 12-8

Server Architecture e-2
SESSIONTIMEZONE Function 16-9
SET Command 7-12
SET Clause 8-15
SET Operators 15-2, 15-3
SET TIME_ZONE Clause 16-9
SET UNUSED Clause 9-26
SET VERIFY ON Command 7-7
Sets of Rows 5-3
Shared Global Area I-23, E-7
Shared SQL Area E-14
Single Ampersand Substitution 7-4

Introduction to Oracle9i: SQL Index-16

S
Single Row Function 3-4
Single Row Operators 6-8
Single Row Subqueries 6-2, 6-7
SMON Process E-8
SOME Operator 6-15
Sorting Results with the ORDER BY Clause 2
Default Sort Order 2-23
Spool File D-5
Structured Query Language (SQL) I-2, I-21, I-22, 1-2, 1-24, 1-25
SQL Buffer C-3
SQL Scripts D-2
SQL*Plus C
SQL*Plus Commands C-2
SQL*Plus Script File 7-3
SQL: 1999 Compliance 4-6, 4-22, 4-30
START Command C-14
START WITH Clause 19-5, 19-6
Statement 1-4
Statement Level Rollback 8-42
STDDEV Function 5-7

Introduction to Oracle9i: SQL Index-17

S
Subqueries 6, 8-16, 8-21, 8-23, 9-18, 11-21, 18-2, 18-3, 18-10
AS Subquery Clause 9-18
Correlated Subquery 18-2, 18-13, 18-14, 18-15, 18-21, 18-24
Correlated UPDATE 18-22
FROM Clause Query 11-21, 18-2, 18-10
Group Functions in a Subquery 6-10
Inner Query 6-3, 6-4, 6-5, 18-5
Multiple Column Subquery 6-7, 18-2, 18-8
Multiple-row Subquery 6-2, 6-7, 6-14, 18-6
Nested Queries 6-4, 18-4
No Rows Returned from the Subquery 6-13
Outer Query 6-5, 18-5
Placement of the Subquery 6-4
Scalar Subquery 18-11
Single Row Subqueries 6-2, 6-7
Subsets, Logical 11-4
Substitution Variables 7-2, 7-3
SUBSTR Function 3-11
SUM Function 5-6, 5-7
Summary Results for Groups of Rows 5-18
Superaggregate Rows 17-7, 17-8, 17-9
SYS Function 9-9
Synonym 9-3, 12-2, 12-3, 12-23, 13-3
SYSDATE Function 3-18, 3-20, 9-7
System Development Life Cycle I-10
System Global Area I-23, E-3, E-8

Introduction to Oracle9i: SQL Index-18

T
Table Aliases 4-12
Table Level Constraints 10-8
Table Prefixes 4-11
Three-Way Join 4-30
Time Zone 16-3
TIMESTAMP Data Type 9-16
TIMESTAMP WITH TIME ZONE 9-15
TIMESTAMP WITH LOCAL TIME 9-16
INTERVAL YEAR TO MONTH 9-17
TIMEZONE_ABBR 16-10
TIMEZONE_REGION 16-10
TO_CHAR Function 3-31, 3-37, 3-39
TO_DATE Function 3-39
TO_NUMBER Function 3-39
TO_TIMESTAMP Function 16-12
TO_YMINTERVAL Function 16-13
Top-n Analysis 11-2, 11-22, 11-23, 11-24
Transactions 8-32
Tree Structured Report 19
TRIM Function 3-11
TRUNC Function 3-15, 3-21, 3-23
TRUNCATE TABLE Statement 9-29
TTITLE Command 7-19
Tuple I-19
TYPE ACCESS_DRIVER_TYPE 20-19
TZOFFSET Function 16-14

Introduction to Oracle9i: SQL Index-19

U
UNDEFINE Command 7-11
UNION Operator 15-7, 15-8, 15-11
UNION Operator 15-10, 15-11
UNIQUE Constraint 10-9, 10-10
Unique Identifier I-18
Unique Index 10-10, 12-6
UPDATE Statement 8, 13-14
SET Clause 8-15
Correlated UPDATE 18-22
UPPER Function 3-9, 3-10
Users - (Creating) 13-6
USER Function 9-7
User Process E-10
USER_CATALOG Dictionary View 9-10
USER_COL_COMMENTS Dictionary View 9-30
USER_COL_PRIVS_MADE Dictionary View D-4
USER_CONS_COLUMNS Dictionary View 10-19, 10-25
USER_CONSTRAINTS Dictionary View 10-4, 10-19, 10-24
USER_DB_LINKS Dictionary View 13-19
USER_INDEXES Dictionary View 12-20
USER_OBJECTS Dictionary View 9-10, d-4
USER_SEQUENCES Dictionary View

12-7

USER_TAB_COMMENTS Dictionary View 9-30
USER_TAB_PRIVS_MADE Dictionary View D-4
USER_TABLES Dictionary View 9-10, D-4
USER_UNUSED_COL_TABS Dictionary View 9-26
USING Clause 4-26, 13-20
UTC (Coordinated Universal Time) 9-15

Introduction to Oracle9i: SQL Index-20

V
VALUES Clause 8-5
Variance 5-7
VERIFY Command 7-7
Views 9-3, 11
Guidelines for Creating a View 11-8
Inline Views 11-2, 11-21
OR REPLACE Clause 11-12
Retrieving Data from a View 11-10
Simple and Complex 11-6
USING Clause 4-26
WITH READ ONLY Clause 11-18
V$TIMEZONE_NAME Dictionary View 16-11
W
WHEN NOT MATCHED Clause 8-31
WHERE Clause 2
Restricting Rows 2-2
Wildcard Symbol 2-12
WITH Clause 18-2, 18-26
WITH CHECK OPTION Clause 8-25, 11-17, 13-13, 13-14, 13-15, 13-18
WITH READ ONLY Clause 11-18
X
XML I-23
Y
Year 2000 Compliance 3-17

Introduction to Oracle9i: SQL Index-21

Introduction to Oracle9i: SQL Index-22



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