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Oracle ® PL/SQL For Dummies ®Published by Wiley Publishing, Inc.. South Proofreaders: Dwight Ramsey, Techbooks Indexer: Techbooks Publishing and Editorial for Technology Dummies Richard

by Michael Rosenblum and Dr Paul Dorsey

PL/SQL

FOR

by Michael Rosenblum and Dr Paul Dorsey

PL/SQL

FOR

Oracle ® PL/SQL For Dummies ®

Published by

Wiley Publishing, Inc.

111 River Street Hoboken, NJ 07030-5774

www.wiley.com

Copyright © 2006 by Wiley Publishing, Inc., Indianapolis, Indiana Published by Wiley Publishing, Inc., Indianapolis, Indiana Published simultaneously in Canada

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About the Authors

Michael Rosenblum is originally from Kremenchuk, Ukraine In 2000, he moved

to the United States, where he lives with his family in Edison, New Jersey Heworks as a Development DBA at Dulcian, Inc Michael is responsible for systemtuning and application architecture He also supports Dulcian developers

by writing complex PL/SQL routines and researching new features He is a frequent presenter at various regional and national Oracle user group confer-ences In his native Ukraine, he received the scholarship of the President ofUkraine, a Masters Degree in Information Systems, and a Diploma with Honorsfrom the Kiev National University of Economics, Ukraine

Dr Paul Dorsey is the founder and President of Dulcian, Inc (www.dulcian.

com), an Oracle consulting firm that specializes in business rules-basedOracle Client-Server and Web custom application development He is thechief architect of Dulcian’s Business Rules Information Manager (BRIM®) tool.Paul is the co-author of seven Oracle Press books that have been translated

into nine languages: Oracle JDeveloper 10g Handbook, Oracle9i JDeveloper

Handbook, Oracle JDeveloper 3 Handbook, Oracle Designer Handbook (2

editions), Oracle Developer Forms and Reports: Advanced Techniques and

Development Standards, Oracle8 Design Using UML Object Modeling In 2003,

he was honored by ODTUG as volunteer of the year, in 2001 by IOUG as

vol-unteer of the year and by Oracle as one of the six initial honorary Oracle 9i

Certified Masters Paul is an Oracle Fusion Middleware Regional Director He

is the President of the New York Oracle Users’ Group and a ContributingEditor of the International Oracle User Group’s SELECT Journal He is also the founder and chairperson of the ODTUG Business Rules Symposium (now called Best Practices Symposium), currently in its sixth year, and the J2EE SIG

Authors’ Acknowledgments

Michael Rosenblum: I would like to thank my co-author, Dr Paul Dorsey (a

well-known guru in the Oracle world), for inviting me to take part in writingthis book and for all his patience working with me for the last five years Also,

I would like to acknowledge the efforts of our project manager, Caryl LeeFisher She not only kept the lazy authors on track, but even managed to convert my not-exactly-native English into something people could read Ofcourse, the book in the form you are reading it would not have been possiblewithout our wonderful technical editor Leslie Tierstein (you can’t imagine thenumber of small “bugs” she discovered in the original drafts) And, last butnot least, love and special thanks to my wife Dora for withstanding the addedpressure on her while I was writing this book

Dr Paul Dorsey: I would first like to acknowledge my co-author Michael

(“Misha”) Rosenblum It is a joy to work with someone possessing such driveand intellect His unwillingness to be sloppy in his code and thinking havegiven not only this book, but all his work, an aspect of excellence all toounusual in this industry I would also like to thank Caryl Lee Fisher (our unac-knowledged “co-author”) Caryl Lee kept Misha and me on track and helpedwordsmith the entire manuscript This is my eighth such collaborationinvolving Caryl Lee, and I can safely say that I am not sure whether I everwould have published even my first book without her assistance She acted

as the intermediary between the excellent editors at Wiley and the authors,thereby averting virtually certain bloodshed She helped to foster the illusionthat we are very easy authors to work with Leslie Tierstein provided heralways impeccable technical edits I have worked with her on a number ofprojects, and she provides many valuable contributions to the finished prod-uct A special thank you goes to my lovely wife Ileana She not only enduredall my time away from home (for the 3 months preceding and following myson’s birth) working on this book, but she also provided serious technicalassistance, since she is a first-rate developer in her own right

Both authors would like to thank their colleagues Mark Hernandez, MarcBacchus, John Rydzy, and Stephen Germany for their help in reviewing thecode samples and text for accuracy

The authors would also like to thank the Wiley team of Rebecca Huehls,Virginia Sanders, Tiffany Ma, and Terri Varveris for their help with this project

Publisher’s Acknowledgments

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Acquisitions, Editorial, and Media Development

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Contents at a Glance

Introduction 1

Part I: Basic PL/SQL Concepts 7

Chapter 1: PL/SQL and Your Database 9

Chapter 2: The PL/SQL Environment 23

Part II: Getting Started with PL/SQL 39

Chapter 3: Laying the Groundwork: PL/SQL Fundamentals 41

Chapter 4: Controlling Program Flow 85

Chapter 5: Handling Exceptions 105

Chapter 6: PL/SQL and SQL Working Together 127

Part III: Standards and Structures 163

Chapter 7: Putting Your Code in the Right Place 165

Chapter 8: Creating Naming Standards 187

Chapter 9: Creating Coding Standards 201

Part IV: PL/SQL Data Manipulations 219

Chapter 10: Basic Datatypes 221

Chapter 11: Advanced Datatypes 253

Part V: Taking PL/SQL to the Next Level 289

Chapter 12: Transaction Control 291

Chapter 13: Dynamic SQL and PL/SQL 313

Chapter 14: PL/SQL Best Practices .335

Part VI: The Part of Tens 355

Chapter 15: Ten PL/SQL Tips 357

Chapter 16: Ten Common Mistakes to Avoid in PL/SQL 377

Index 397

Table of Contents

Introduction 1

About This Book 1

Foolish Assumptions 2

How This Book Is Organized 2

Part I: Basic PL/SQL Concepts 2

Part II: Getting Started with PL/SQL 3

Part III: Standards and Structures 3

Part IV: PL/SQL Data Manipulations 3

Part V: Taking PL/SQL to the Next Level 3

Part VI: The Part of Tens 4

Icons Used in This Book 4

Where to Go from Here 4

Part I: Basic PL/SQL Concepts 7

Chapter 1: PL/SQL and Your Database 9

Knowing Just Enough about Relational Databases 9

What makes a database “relational”? 10

Understanding basic database terminology 12

Introducing database normalization 13

What is a DBMS? 16

The Scoop on SQL and PL/SQL 16

The purpose of SQL and PL/SQL 17

The difference between SQL and PL/SQL 18

What’s new in Oracle SQL and PL/SQL? 18

What Is PL/SQL Good For? 19

Using database triggers 19

Scripting with speed 20

Keeping code server-side 20

Programming for Oracle Developer 21

Chapter 2: The PL/SQL Environment 23

Setting Up an Oracle Environment 23

Hardware and Software Requirements 25

Accessing the Oracle Technology Network 26

Installing the Database 27

Working with Code 28

SQL*Plus 28

Oracle SQL Developer 30

Third-party tools 30

Establishing a Database Connection 31

Checking the operating services 32

Connecting with your username 32

Unlocking (or locking) accounts 33

Resetting passwords 33

Setting up the server to communicate 34

The Basics of PL/SQL Programs 34

Writing a simple program 34

Creating stored procedures 36

Passing parameters to procedures 36

Examining the Sample Data 37

The Scott/Tiger schema 37

The Human Resources (HR) and Order Entry (OE) schemas 38

Part II: Getting Started with PL/SQL 39

Chapter 3: Laying the Groundwork: PL/SQL Fundamentals 41

PL/SQL As a Programming Language 41

Anonymous PL/SQL Blocks 42

Introducing the Lexical Set of Elements 43

Identifiers 44

Delimiters 44

Literals 45

Comments 45

Working with Constants and Variables 46

Declaring variables 46

Assigning values to variables 48

Literals as variable values 49

Understanding the scope of variables 51

Building Expressions with Operators 53

Running Anonymous Blocks of Code 56

Identifying common mistakes 56

Spotting compilation errors 57

Recognizing semicolon-related errors 57

Creating Reusable PL/SQL Code 59

Wrapping a task into a procedure 59

Returning values with functions 61

Parameters of subprograms 63

Storing PL/SQL in the Database 67

Database procedures and functions 68

Packages 69

Triggers 71

Interpreting and fixing compilation errors 73

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Checking Out PL/SQL Extras 76

Overloading calls 76

Resolving calls to subprograms 78

Recursion 80

Compiler hints and directives 82

Built-in packages 83

Chapter 4: Controlling Program Flow 85

Creating Condition Statements 85

IF THEN statements 86

IF ELSE statements 87

CASE statements 89

Comparing with NULL 91

Handling conditions 95

Looping the Loop 97

Simple loops 97

Nested loops 99

WHILE loop 100

FOR loop 102

Chapter 5: Handling Exceptions 105

Understanding Exception Basics 106

Adding Exception Handlers to Your Code 107

Understanding Different Exception Types 110

Predefined Exceptions in PL/SQL Code 111

Adding User-Defined Exceptions 114

Assigning a code to a user-defined exception 115

Including error messages in user-defined exceptions 116

Propagation of Exceptions 118

Seeing propagation of exceptions in action 118

Handling exceptions without halting the program 122

Avoiding exceptions raised in declaration part and exception handler 124

Writing Exceptional Exceptions 126

Chapter 6: PL/SQL and SQL Working Together 127

Cursors: What They Are and How to Use Them 128

Returning more than one piece of information 129

Looping through multiple records 132

Placing cursors in nested loops 133

Passing parameters to cursors 134

Knowing Where to Declare Cursors 137

Defining cursors in the header of the program unit 138

Defining cursors in the local PL/SQL block 138

Defining cursors in the package body 139

Defining cursors in the package spec 140

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Table of Contents

Being Explicitly Smart with Implicit Cursors 142

Retrieving a single row: The basic syntax 142

Handling exceptions in implicit cursors 143

Returning an implicit cursor into a record 143

Accessing Status Info by Using Cursor Variables 144

Checking the status of explicit cursors 145

Checking the status of implicit cursors 146

Updating Records Fetched from Cursors 148

Using a simple UPDATE statement 148

Updating with logical operators 148

Taking a Shortcut with CURSOR FOR Loops 150

Comparing CURSOR FOR loops to cursors with the LOOP command 150

When do CURSOR FOR loops simplify exception handling? 152

When CURSOR FOR loops make your life harder 153

Knowing what record is processing 155

Referencing Functions in SQL 155

Important facts to remember 157

Getting good performance with functions 160

Part III: Standards and Structures 163

Chapter 7: Putting Your Code in the Right Place 165

Putting Code in the Database 165

Managing code 166

Packaging code in the database 166

Placing triggers on tables 174

Building INSTEAD OF trigger views 177

Advantages of putting code in the database 182

Disadvantages of putting code in the database 182

Putting Code in the Application Server (Middle-Tier Approach) 183

Advantages of the middle-tier approach 184

Disadvantages of the middle-tier approach 184

Placing code in the view layer 185

Where Should You Place the Business Logic? 185

Chapter 8: Creating Naming Standards 187

What’s in a Naming Standard? 187

Oracle database influences 188

Java influences 188

Modern application development tools and their influences 189

Setting Naming Standards for Common Code Elements 189

Basic objects 190

Variables 191

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