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Oracle® Database

PL/SQL User's Guide and Reference

10g Release 2 (10.2)

B14261-01

June 2005

Oracle Database PL/SQL User's Guide and Reference 10g Release 2 (10.2)

B14261-01

Copyright © 1996, 2005, Oracle. All rights reserved.

Contributors: Shashaanka Agrawal, Cailein Barclay, Eric Belden, Dmitri Bronnikov, Sharon Castledine,

Thomas Chang, Ravindra Dani, Chandrasekharan Iyer, Susan Kotsovolos, Neil Le, Warren Li, Bryn Llewellyn, Valarie Moore, Chris Racicot, Murali Vemulapati, John Russell, Guhan Viswanathan, Minghui Yang

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Contents

Send Us Your Comments ..................................................................................................................... xvii

Preface............................................................................................................................................................... xix

Audience..................................................................................................................................................... xix

Documentation Accessibility................................................................................................................... xix

Structure ..................................................................................................................................................... xx

PL/SQL Sample Programs....................................................................................................................... xxi

Related Documents.................................................................................................................................. xxii

Conventions .............................................................................................................................................. xxii

What's New in PL/SQL?......................................................................................................................... xxv

New Features in PL/SQL for Oracle Database 10g Release 2 (10.2)................................................ xxv

New Features in PL/SQL for Oracle Database 10g Release 1 (10.1)................................................ xxvi

1 Overview of PL/SQL

Advantages of PL/SQL............................................................................................................................ 1-1

Tight Integration with SQL............................................................................................................... 1-2

Better Performance............................................................................................................................. 1-2

Higher Productivity........................................................................................................................... 1-3

Full Portability.................................................................................................................................... 1-3

Tight Security...................................................................................................................................... 1-3

Access to Pre-defined Packages....................................................................................................... 1-4

Support for Object-Oriented Programming................................................................................... 1-4

Support for Developing Web Applications and Pages................................................................. 1-4

Understanding the Main Features of PL/SQL.................................................................................... 1-4

Understanding PL/SQL Block Structure........................................................................................ 1-4

Understanding PL/SQL Variables and Constants........................................................................ 1-5

Declaring Variables..................................................................................................................... 1-5

Assigning Values to a Variable................................................................................................. 1-6

Bind Variables ............................................................................................................................. 1-7

Declaring Constants.................................................................................................................... 1-7

Processing Queries with PL/SQL.................................................................................................... 1-8

Declaring PL/SQL Subprograms..................................................................................................... 1-8

Declaring Datatypes for PL/SQL Variables................................................................................... 1-8

%TYPE.......................................................................................................................................... 1-8

iv

%ROWTYPE ................................................................................................................................ 1-9

Understanding PL/SQL Control Structures.................................................................................. 1-9

Conditional Control................................................................................................................. 1-10

Iterative Control....................................................................................................................... 1-10

Sequential Control ................................................................................................................... 1-12

Understanding Conditional Compilation ................................................................................... 1-12

Writing Reusable PL/SQL Code................................................................................................... 1-13

Subprograms: Procedures and Functions ............................................................................ 1-13

Packages: APIs Written in PL/SQL....................................................................................... 1-13

Inputting and Outputting Data with PL/SQL............................................................................ 1-15

Understanding PL/SQL Data Abstraction.................................................................................. 1-16

Cursors ...................................................................................................................................... 1-16

Collections................................................................................................................................. 1-16

Records...................................................................................................................................... 1-16

Object Types ............................................................................................................................. 1-17

Understanding PL/SQL Error Handling .................................................................................... 1-18

PL/SQL Architecture............................................................................................................................. 1-18

In the Oracle Database Server....................................................................................................... 1-19

Anonymous Blocks.................................................................................................................. 1-19

Stored Subprograms................................................................................................................ 1-19

Database Triggers .................................................................................................................... 1-20

In Oracle Tools................................................................................................................................. 1-21

2 Fundamentals of the PL/SQL Language

Character Sets and Lexical Units........................................................................................................... 2-1

Delimiters............................................................................................................................................ 2-2

Identifiers ............................................................................................................................................ 2-3

Reserved Words.......................................................................................................................... 2-4

Predefined Identifiers................................................................................................................. 2-4

Quoted Identifiers....................................................................................................................... 2-4

Literals ................................................................................................................................................. 2-4

Numeric Literals.......................................................................................................................... 2-5

Character Literals........................................................................................................................ 2-6

String Literals............................................................................................................................... 2-6

BOOLEAN Literals..................................................................................................................... 2-7

Datetime Literals......................................................................................................................... 2-7

Comments ........................................................................................................................................... 2-7

Single-Line Comments............................................................................................................... 2-7

Multi-line Comments ................................................................................................................. 2-8

Restrictions on Comments......................................................................................................... 2-8

Declarations............................................................................................................................................... 2-8

Constants............................................................................................................................................. 2-9

Using DEFAULT................................................................................................................................ 2-9

Using NOT NULL.............................................................................................................................. 2-9

Using the %TYPE Attribute........................................................................................................... 2-10

Using the %ROWTYPE Attribute................................................................................................. 2-11

Aggregate Assignment............................................................................................................ 2-12

v

Using Aliases............................................................................................................................ 2-12

Restrictions on Declarations.......................................................................................................... 2-13

PL/SQL Naming Conventions............................................................................................................ 2-13

Scope and Visibility of PL/SQL Identifiers..................................................................................... 2-15

Assigning Values to Variables............................................................................................................ 2-18

Assigning BOOLEAN Values........................................................................................................ 2-19

Assigning a SQL Query Result to a PL/SQL Variable.............................................................. 2-19

PL/SQL Expressions and Comparisons............................................................................................. 2-19

Logical Operators............................................................................................................................ 2-20

Order of Evaluation................................................................................................................. 2-21

Short-Circuit Evaluation......................................................................................................... 2-21

Comparison Operators............................................................................................................ 2-22

Relational Operators................................................................................................................ 2-22

IS NULL Operator.................................................................................................................... 2-23

LIKE Operator.......................................................................................................................... 2-23

BETWEEN Operator................................................................................................................ 2-23

IN Operator............................................................................................................................... 2-23

Concatenation Operator.......................................................................................................... 2-23

BOOLEAN Expressions ................................................................................................................. 2-24

BOOLEAN Arithmetic Expressions...................................................................................... 2-24

BOOLEAN Character Expressions........................................................................................ 2-24

BOOLEAN Date Expressions................................................................................................. 2-25

Guidelines for PL/SQL BOOLEAN Expressions................................................................ 2-25

CASE Expressions........................................................................................................................... 2-26

Simple CASE expression......................................................................................................... 2-26

Searched CASE Expression .................................................................................................... 2-27

Handling Null Values in Comparisons and Conditional Statements..................................... 2-27

NULLs and the NOT Operator.............................................................................................. 2-28

Conditional Compilation..................................................................................................................... 2-30

How Does Conditional Compilation Work?............................................................................... 2-31

Conditional Compilation Control Tokens............................................................................ 2-31

Using Conditional Compilation Selection Directives......................................................... 2-31

Using Conditional Compilation Error Directives ............................................................... 2-31

Using Conditional Compilation Inquiry Directives ........................................................... 2-31

Using Predefined Inquiry Directives With Conditional Compilation ............................ 2-32

Using Static Expressions with Conditional Compilation................................................... 2-33

Setting the PLSQL_CCFLAGS Initialization Parameter..................................................... 2-34

Using DBMS_DB_VERSION Package Constants................................................................ 2-35

Conditional Compilation Examples............................................................................................. 2-35

Using Conditional Compilation to Specify Code for Database Versions........................ 2-35 Using DBMS_PREPROCESSOR Procedures to Print or Retrieve Source Text............... 2-36

Conditional Compilation Restrictions.......................................................................................... 2-37

Using PL/SQL to Create Web Applications and Server Pages...................................................... 2-38

PL/SQL Web Applications............................................................................................................ 2-38

PL/SQL Server Pages..................................................................................................................... 2-38

Summary of PL/SQL Built-In Functions........................................................................................... 2-38

vi

3 PL/SQL Datatypes

Overview of Predefined PL/SQL Datatypes....................................................................................... 3-1

PL/SQL Number Types.................................................................................................................... 3-2

BINARY_INTEGER Datatype................................................................................................... 3-2

BINARY_FLOAT and BINARY_DOUBLE Datatypes........................................................... 3-2

NUMBER Datatype .................................................................................................................... 3-3

PLS_INTEGER Datatype............................................................................................................ 3-4

PL/SQL Character and String Types.............................................................................................. 3-4

CHAR Datatype......................................................................................................................... 3-4

LONG and LONG RAW Datatypes......................................................................................... 3-5

RAW Datatype ............................................................................................................................ 3-6

ROWID and UROWID Datatype.............................................................................................. 3-6

VARCHAR2 Datatype................................................................................................................ 3-8

PL/SQL National Character Types................................................................................................. 3-9

Comparing UTF8 and AL16UTF16 Encodings....................................................................... 3-9

NCHAR Datatype....................................................................................................................... 3-9

NVARCHAR2 Datatype......................................................................................................... 3-10

PL/SQL LOB Types........................................................................................................................ 3-10

BFILE Datatype ........................................................................................................................ 3-11

BLOB Datatype......................................................................................................................... 3-11

CLOB Datatype ........................................................................................................................ 3-11

NCLOB Datatype..................................................................................................................... 3-12

PL/SQL Boolean Types.................................................................................................................. 3-12

BOOLEAN Datatype............................................................................................................... 3-12

PL/SQL Date, Time, and Interval Types..................................................................................... 3-12

DATE Datatype........................................................................................................................ 3-13

TIMESTAMP Datatype ........................................................................................................... 3-13

TIMESTAMP WITH TIME ZONE Datatype........................................................................ 3-14

TIMESTAMP WITH LOCAL TIME ZONE Datatype......................................................... 3-15

INTERVAL YEAR TO MONTH Datatype........................................................................... 3-16

INTERVAL DAY TO SECOND Datatype............................................................................ 3-16

Datetime and Interval Arithmetic................................................................................................. 3-17

Avoiding Truncation Problems Using Date and Time Subtypes............................................. 3-17

Overview of PL/SQL Subtypes........................................................................................................... 3-17

Defining Subtypes .......................................................................................................................... 3-18

Using Subtypes................................................................................................................................ 3-18

Type Compatibility With Subtypes....................................................................................... 3-19

Constraints and Default Values With Subtypes.................................................................. 3-20

Converting PL/SQL Datatypes........................................................................................................... 3-21

Explicit Conversion......................................................................................................................... 3-21

Implicit Conversion ........................................................................................................................ 3-21

Choosing Between Implicit and Explicit Conversion................................................................ 3-23

DATE Values ................................................................................................................................... 3-23

RAW and LONG RAW Values..................................................................................................... 3-23

Differences between the CHAR and VARCHAR2 Datatypes...................................................... 3-23

Assigning Character Values .......................................................................................................... 3-23

Comparing Character Values........................................................................................................ 3-24

vii

Inserting Character Values ............................................................................................................ 3-25

Selecting Character Values ............................................................................................................ 3-26

4 Using PL/SQL Control Structures

Overview of PL/SQL Control Structures............................................................................................. 4-1

Testing Conditions: IF and CASE Statements.................................................................................... 4-2

Using the IF-THEN Statement ......................................................................................................... 4-2

Using the IF-THEN-ELSE Statement............................................................................................... 4-2

Using the IF-THEN-ELSIF Statement.............................................................................................. 4-3

Using CASE Statements.................................................................................................................... 4-4

Searched CASE Statement......................................................................................................... 4-5

Guidelines for PL/SQL Conditional Statements........................................................................... 4-6

Controlling Loop Iterations: LOOP and EXIT Statements............................................................... 4-7

Using the LOOP Statement............................................................................................................... 4-7

Using the EXIT Statement................................................................................................................. 4-7

Using the EXIT-WHEN Statement................................................................................................... 4-8

Labeling a PL/SQL Loop.................................................................................................................. 4-8

Using the WHILE-LOOP Statement................................................................................................ 4-9

Using the FOR-LOOP Statement ..................................................................................................... 4-9

How PL/SQL Loops Iterate ................................................................................................... 4-10

Dynamic Ranges for Loop Bounds........................................................................................ 4-11

Scope of the Loop Counter Variable ..................................................................................... 4-11

Using the EXIT Statement in a FOR Loop............................................................................ 4-12

Sequential Control: GOTO and NULL Statements........................................................................ 4-13

Using the GOTO Statement........................................................................................................... 4-13

Restrictions on the GOTO Statement.................................................................................... 4-15

Using the NULL Statement............................................................................................................ 4-15

5 Using PL/SQL Collections and Records

What are PL/SQL Collections and Records?....................................................................................... 5-1

Understanding PL/SQL Collections............................................................................................... 5-2

Understanding Nested Tables................................................................................................... 5-2

Understanding Varrays.............................................................................................................. 5-3

Understanding Associative Arrays (Index-By Tables).......................................................... 5-3

How Globalization Settings Affect VARCHAR2 Keys for Associative Arrays................. 5-4

Understanding PL/SQL Records..................................................................................................... 5-5

Choosing Which PL/SQL Collection Types to Use............................................................................ 5-5

Choosing Between Nested Tables and Associative Arrays......................................................... 5-5

Choosing Between Nested Tables and Varrays............................................................................. 5-5

Defining Collection Types and Declaring Collection Variables..................................................... 5-6

Declaring PL/SQL Collection Variables......................................................................................... 5-7

Initializing and Referencing Collections......................................................................................... 5-10

Referencing Collection Elements.................................................................................................. 5-11

Assigning Collections........................................................................................................................... 5-12

Comparing Collections......................................................................................................................... 5-16

Using Multilevel Collections.............................................................................................................. 5-18

viii

Using Collection Methods................................................................................................................... 5-19

Checking If a Collection Element Exists (EXISTS Method) ...................................................... 5-19

Counting the Elements in a Collection (COUNT Method)....................................................... 5-20

Checking the Maximum Size of a Collection (LIMIT Method)................................................ 5-20

Finding the First or Last Collection Element (FIRST and LAST Methods) ............................ 5-21

Looping Through Collection Elements (PRIOR and NEXT Methods).................................... 5-22

Increasing the Size of a Collection (EXTEND Method)............................................................. 5-23

Decreasing the Size of a Collection (TRIM Method).................................................................. 5-24

Deleting Collection Elements (DELETE Method) ...................................................................... 5-25

Applying Methods to Collection Parameters.............................................................................. 5-26

Avoiding Collection Exceptions......................................................................................................... 5-27

Defining and Declaring Records........................................................................................................ 5-29

Using Records as Procedure Parameters and Function Return Values.................................. 5-31

Assigning Values to Records............................................................................................................... 5-32

Comparing Records........................................................................................................................ 5-33

Inserting PL/SQL Records into the Database............................................................................. 5-33

Updating the Database with PL/SQL Record Values............................................................... 5-34

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