PL/SQL
User's Guide and Reference
10g Release 1 (10.1)
Part No. B10807-01
December 2003
PL/SQL User's Guide and Reference, 10g Release 1 (10.1)
Part No. B10807-01
Copyright © 1996, 2003 Oracle. All rights reserved.
Primary Author: John Russell
Contributors: Shashaanka Agrawal, Cailein Barclay, Dmitri Bronnikov, Sharon Castledine, Thomas
Chang, Ravindra Dani, Chandrasekharan Iyer, Susan Kotsovolos, Neil Le, Warren Li, Bryn Llewellyn, Chris
Racicot, Murali Vemulapati, Guhan Viswanathan, Minghui Yang
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Contents
Send Us Your Comments ...................................................................................................................... xv
Preface.............................................................................................................................................................. xvii
Audience.................................................................................................................................................... xvii
How This Book Is Organized.................................................................................................................. xvii
Related Documentation........................................................................................................................... xix
Conventions ............................................................................................................................................... xx
Sample Database Tables .......................................................................................................................... xxi
Documentation Accessibility.................................................................................................................. xxii
Reading the Syntax Diagrams ................................................................................................................ xxii
What's New in PL/SQL?......................................................................................................................... xxiii
New Features in PL/SQL for Oracle Database 10g ........................................................................... xxiii
New Features in PL/SQL for Oracle9i................................................................................................ xxvi
1 Overview of PL/SQL
Advantages of PL/SQL ............................................................................................................................ 1-1
Tight Integration with SQL .............................................................................................................. 1-1
Support for SQL.................................................................................................................................. 1-2
Better Performance............................................................................................................................. 1-2
Higher Productivity........................................................................................................................... 1-3
Full Portability.................................................................................................................................... 1-3
Tight Security...................................................................................................................................... 1-3
Support for Object-Oriented Programming................................................................................... 1-3
Understanding the Main Features of PL/SQL .................................................................................... 1-4
Block Structure.................................................................................................................................... 1-4
Variables and Constants.................................................................................................................... 1-5
Processing Queries with PL/SQL.................................................................................................... 1-6
Declaring PL/SQL Variables............................................................................................................ 1-6
Control Structures.............................................................................................................................. 1-7
Writing Reusable PL/SQL Code...................................................................................................... 1-9
Data Abstraction.............................................................................................................................. 1-10
Error Handling ................................................................................................................................ 1-12
PL/SQL Architecture............................................................................................................................. 1-12
In the Oracle Database Server ....................................................................................................... 1-13
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In Oracle Tools................................................................................................................................. 1-14
2 Fundamentals of the PL/SQL Language
Character Set.............................................................................................................................................. 2-1
Lexical Units .............................................................................................................................................. 2-1
Delimiters ............................................................................................................................................ 2-2
Identifiers............................................................................................................................................. 2-3
Literals ................................................................................................................................................. 2-4
Comments ........................................................................................................................................... 2-7
Declarations............................................................................................................................................... 2-8
Using DEFAULT ................................................................................................................................ 2-9
Using NOT NULL.............................................................................................................................. 2-9
Using the %TYPE Attribute.............................................................................................................. 2-9
Using the %ROWTYPE Attribute ................................................................................................. 2-10
Restrictions on Declarations .......................................................................................................... 2-12
PL/SQL Naming Conventions ............................................................................................................ 2-12
Scope and Visibility of PL/SQL Identifiers...................................................................................... 2-14
Assigning Values to Variables ............................................................................................................ 2-16
Assigning Boolean Values ............................................................................................................. 2-17
Assigning a SQL Query Result to a PL/SQL Variable .............................................................. 2-17
PL/SQL Expressions and Comparisons............................................................................................. 2-17
Logical Operators............................................................................................................................ 2-18
Boolean Expressions ....................................................................................................................... 2-21
CASE Expressions........................................................................................................................... 2-24
Handling Null Values in Comparisons and Conditional Statements ..................................... 2-25
Summary of PL/SQL Built-In Functions........................................................................................... 2-28
3 PL/SQL Datatypes
Overview of Predefined PL/SQL Datatypes........................................................................................ 3-1
PL/SQL Number Types.................................................................................................................... 3-2
PL/SQL Character and String Types .............................................................................................. 3-4
PL/SQL National Character Types ................................................................................................. 3-8
PL/SQL LOB Types........................................................................................................................ 3-10
PL/SQL Boolean Types.................................................................................................................. 3-11
PL/SQL Date, Time, and Interval Types..................................................................................... 3-12
Datetime and Interval Arithmetic................................................................................................. 3-15
Avoiding Truncation Problems Using Date and Time Subtypes............................................. 3-16
Overview of PL/SQL Subtypes .......................................................................................................... 3-16
Defining Subtypes .......................................................................................................................... 3-16
Using Subtypes ............................................................................................................................... 3-17
Converting PL/SQL Datatypes............................................................................................................ 3-18
Explicit Conversion......................................................................................................................... 3-18
Implicit Conversion ........................................................................................................................ 3-18
Choosing Between Implicit and Explicit Conversion................................................................ 3-20
DATE Values.................................................................................................................................... 3-20
RAW and LONG RAW Values ..................................................................................................... 3-20
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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 the CASE Statement ............................................................................................................... 4-3
Guidelines for PL/SQL Conditional Statements........................................................................... 4-5
Controlling Loop Iterations: LOOP and EXIT Statements............................................................... 4-6
Using the LOOP Statement............................................................................................................... 4-6
Using the EXIT Statement................................................................................................................. 4-7
Using the EXIT-WHEN Statement................................................................................................... 4-7
Labeling a PL/SQL Loop.................................................................................................................. 4-7
Using the WHILE-LOOP Statement................................................................................................ 4-8
Using the FOR-LOOP Statement ..................................................................................................... 4-9
Sequential Control: GOTO and NULL Statements ........................................................................ 4-12
Using the GOTO Statement ........................................................................................................... 4-12
Using the NULL Statement............................................................................................................ 4-13
5 Using PL/SQL Collections and Records
What Is a Collection? ............................................................................................................................... 5-1
Understanding Nested Tables.......................................................................................................... 5-2
Understanding Varrays..................................................................................................................... 5-2
Understanding Associative Arrays (Index-By Tables) ................................................................. 5-3
How Globalization Settings Affect VARCHAR2 Keys for Associative Arrays ........................ 5-4
Choosing Which PL/SQL Collection Types to Use ............................................................................ 5-4
Choosing Between Nested Tables and Associative Arrays ......................................................... 5-5
Choosing Between Nested Tables and Varrays............................................................................. 5-5
Defining Collection Types ...................................................................................................................... 5-6
Defining SQL Types Equivalent to PL/SQL Collection Types ................................................... 5-7
Declaring PL/SQL Collection Variables............................................................................................... 5-8
Initializing and Referencing Collections ......................................................................................... 5-10
Referencing Collection Elements .................................................................................................. 5-12
Assigning Collections........................................................................................................................... 5-13
Comparing Collections......................................................................................................................... 5-16
Using PL/SQL Collections with SQL Statements ........................................................................... 5-17
Using PL/SQL Varrays with INSERT, UPDATE, and SELECT Statements .......................... 5-20
Manipulating Individual Collection Elements with SQL.......................................................... 5-21
Using Multilevel Collections .............................................................................................................. 5-21
Using Collection Methods................................................................................................................... 5-23
Checking If a Collection Element Exists (EXISTS Method) ...................................................... 5-24
Counting the Elements in a Collection (COUNT Method)....................................................... 5-24
Checking the Maximum Size of a Collection (LIMIT Method) ................................................ 5-24
Finding the First or Last Collection Element (FIRST and LAST Methods) ............................ 5-25
Looping Through Collection Elements (PRIOR and NEXT Methods).................................... 5-26
Increasing the Size of a Collection (EXTEND Method)............................................................. 5-27
