PL/SQL User’s Guide and Reference - Oracle

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

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