Oracle PL/SQL. DUMmIES. by Michael Rosenblum and Dr. Paul Dorsey FOR

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1 Oracle PL/SQL FOR DUMmIES by Michael Rosenblum and Dr. Paul Dorsey

2 Oracle PL/SQL For Dummies Published by Wiley Publishing, Inc. 111 River Street Hoboken, NJ Copyright 2006 by Wiley Publishing, Inc., Indianapolis, Indiana Published by Wiley Publishing, Inc., Indianapolis, Indiana Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) , fax (978) Requests to the Publisher for permission should be addressed to the Legal Department, Wiley Publishing, Inc., Crosspoint Blvd., Indianapolis, IN 46256, (317) , fax (317) , or online at Trademarks: Wiley, the Wiley Publishing logo, For Dummies, the Dummies Man logo, A Reference for the Rest of Us!, The Dummies Way, Dummies Daily, The Fun and Easy Way, Dummies.com, and related trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates in the United States and other countries, and may not be used without written permission. Oracle is a registered trademark of Oracle Corporation. All other trademarks are the property of their respective owners. Wiley Publishing, Inc., is not associated with any product or vendor mentioned in this book. LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: THE PUBLISHER AND THE AUTHOR MAKE NO REP- RESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CON- TENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CRE- ATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CON- TAINED HEREIN MAY NOT BE SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOR THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A POTENTIAL SOURCE OF FUR- THER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFOR- MATION THE ORGANIZATION OR WEBSITE MAY PROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ. For general information on our other products and services, please contact our Customer Care Department within the U.S. at , outside the U.S. at , or fax For technical support, please visit Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Library of Congress Control Number: ISBN-13: ISBN-10: Manufactured in the United States of America O/RX/QV/QW/IN

3 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 Chapter 6: PL/SQL and SQL Working Together Part III: Standards and Structures Chapter 7: Putting Your Code in the Right Place Chapter 8: Creating Naming Standards Chapter 9: Creating Coding Standards Part IV: PL/SQL Data Manipulations Chapter 10: Basic Datatypes Chapter 11: Advanced Datatypes Part V: Taking PL/SQL to the Next Level Chapter 12: Transaction Control Chapter 13: Dynamic SQL and PL/SQL Chapter 14: PL/SQL Best Practices Part VI: The Part of Tens Chapter 15: Ten PL/SQL Tips Chapter 16: Ten Common Mistakes to Avoid in PL/SQL Index...397

4 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 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 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

5 x Oracle PL/SQL For Dummies 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 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

6 Table of Contents xi 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 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 FOR loop Chapter 5: Handling Exceptions Understanding Exception Basics Adding Exception Handlers to Your Code Understanding Different Exception Types Predefined Exceptions in PL/SQL Code Adding User-Defined Exceptions Assigning a code to a user-defined exception Including error messages in user-defined exceptions Propagation of Exceptions Seeing propagation of exceptions in action Handling exceptions without halting the program Avoiding exceptions raised in declaration part and exception handler Writing Exceptional Exceptions Chapter 6: PL/SQL and SQL Working Together Cursors: What They Are and How to Use Them Returning more than one piece of information Looping through multiple records Placing cursors in nested loops Passing parameters to cursors Knowing Where to Declare Cursors Defining cursors in the header of the program unit Defining cursors in the local PL/SQL block Defining cursors in the package body Defining cursors in the package spec...140

7 xii Oracle PL/SQL For Dummies Being Explicitly Smart with Implicit Cursors Retrieving a single row: The basic syntax Handling exceptions in implicit cursors Returning an implicit cursor into a record Accessing Status Info by Using Cursor Variables Checking the status of explicit cursors Checking the status of implicit cursors Updating Records Fetched from Cursors Using a simple UPDATE statement Updating with logical operators Taking a Shortcut with CURSOR FOR Loops Comparing CURSOR FOR loops to cursors with the LOOP command When do CURSOR FOR loops simplify exception handling? When CURSOR FOR loops make your life harder Knowing what record is processing Referencing Functions in SQL Important facts to remember Getting good performance with functions Part III: Standards and Structures Chapter 7: Putting Your Code in the Right Place Putting Code in the Database Managing code Packaging code in the database Placing triggers on tables Building INSTEAD OF trigger views Advantages of putting code in the database Disadvantages of putting code in the database Putting Code in the Application Server (Middle-Tier Approach) Advantages of the middle-tier approach Disadvantages of the middle-tier approach Placing code in the view layer Where Should You Place the Business Logic? Chapter 8: Creating Naming Standards What s in a Naming Standard? Oracle database influences Java influences Modern application development tools and their influences Setting Naming Standards for Common Code Elements Basic objects Variables...191

8 Table of Contents xiii Program units: Procedures, packages, functions, triggers Parameters in code objects Exceptions User-defined datatypes Collections Filenames Making Sure Your Organization Follows Standards Chapter 9: Creating Coding Standards Why Standards Are Important Universal Truths Don t hard-code any constant value Don t make your program units too big or too small Put each data element on its own line Too many comments are much better than too few comments Avoid global variables Indent carefully Be careful with capitalization Use generic variable datatype declarations Limit line length Use explicit data conversion for dates Use synonyms Developing SQL Code Consistently Using a new line Using explicit column lists Prefixing (and suffixing) column names from multiple tables Giving columns aliases Using parentheses in complex mathematical and logical expressions Using white space intelligently Writing save exception handlers Packaging stored program units Part IV: PL/SQL Data Manipulations Chapter 10: Basic Datatypes Introducing the Main Datatype Groups Working with Numeric Datatypes Using the NUMBER datatype Boosting performance with BINARY_INTEGER Using BINARY_FLOAT and BINARY_DOUBLE for complex calculations...226

9 xiv Oracle PL/SQL For Dummies Handling numeric datatypes in built-in functions Keeping Track of Date and Time Selecting the info you want from DATE Using TIMESTAMP Using TIMESTAMP WITH TIME ZONE Storing elapsed time with INTERVAL Working with dates and built-in functions Storing Logical Values with BOOLEAN Processing Characters and Strings Limiting variable length with CHAR versus VARCHAR Useful character built-in functions Extending your options with regular expressions Chapter 11: Advanced Datatypes Handling Large Objects in the Database Using internal large objects (CLOB, BLOB) Creating pointers with external large objects Working with Large Objects Populating BFILE Loading data to the CLOB by using BFILE Loading a page to a BLOB Performing basic string operations on CLOBs Keeping Code Consistent with User-Defined Subtypes Defining Your Own Datatypes Records Object types Grouping Sets of Data into Collections Using VARRAYs Nesting variable data sets in tables Associative arrays (index-by tables) Speeding Up Data Collection with Bulk Operations Using the BULK COLLECT command Adding a limit to BULK COLLECT Part V: Taking PL/SQL to the Next Level Chapter 12: Transaction Control Using Transactions to Maintain Data Consistency Committing or Rolling Back Changes to the Database Firing explicit and implicit commits Rolling back changes Knowing when to use implicit rollbacks Resolving deadlocks...298

10 Table of Contents xv Autonomous Transactions Setting up the syntax for an autonomous transaction Handling auditing and security with autonomous transactions Autonomous transaction features Applying autonomous transactions to other real-world situations Chapter 13: Dynamic SQL and PL/SQL Taking Advantage of Dynamic SQL A Simple EXECUTE IMMEDIATE Building SQL on the Fly Improve performance with bind variables Return information using cursor variables Building DDL on the Fly Using Quoted Strings with Dynamic SQL Working with Advanced Datatypes Using BULK COLLECT with dynamic SQL Dynamic OPEN...FOR Chapter 14: PL/SQL Best Practices Why Are Best Practices Important? Laying the Groundwork for Good Coding Understanding the big picture Communicating effectively Creating a code specification Writing Code with Best Practices in Mind Stub out your code Check the architecture as you go Prove code works with test cases Use code libraries Keep the code maintainable Don t forget about performance Compile as you go Debug the timesaving way Testing Your Code What are you testing? Creating a testing architecture Performance and load testing Tuning performance Good enough is best Coding the Agile Way Working together in Agile teams Programming in pairs Delivering code quickly Test first...351

Beginning Transact-SQL with SQL Server 2000 and Paul Turley with Dan Wood

Beginning Transact-SQL with SQL Server 2000 and 2005 Paul Turley with Dan Wood Beginning Transact-SQL with SQL Server 2000 and 2005 Beginning Transact-SQL with SQL Server 2000 and 2005 Paul Turley with