Oracle PL/SQL INTERACTIVE WORKBOOK

Transcription

1 Oracle PL/SQL INTERACTIVE WORKBOOK

2 BOOKS IN THIS SERIES Baman Motivala Oracle Forms Interactive Workbook Benjamin Rosenzweig & Elena Silvestrova Oracle PL/SQL Interactive Workbook Alex Morrison & Alice Rischert Oracle SQL Interactive Workbook

3 Oracle PL/SQL INTERACTIVE WORKBOOK BENJAMIN ROSENZWEIG ELENA SILVESTROVA Prentice Hall PTR Upper Saddle River, New Jersey

4 Library of Congress Cataloging-in-Publication Data Rosenzweig, Benjamin. Oracle PL/SQL interactive workbook / Benjamin Rosenzweig, Elena Silvestrova. p. cm. ISBN PL/SQL (Computer program language) 2. Oracle (Computer file) 3. Relational databases. I. Silvestrova, Elena. II. Title. QA76.73.P258 R dc Acquisitions editor: Tim Moore Development editor: Russ Hall Marketing manager: Bryan Gambrel Buyer: Maura Goldstaub Editorial Assistant: Julie Okulicz Cover design director: Jerry Votta Cover designer: Nina Scuderi Art director: Gail Cocker-Bogusz Series design: Meryl Poweski Project coordinator: Anne Trowbridge Web site project manager: Eileen Clark Compositor/Production services: Pine Tree Composition, Inc by Prentice-Hall PTR Prentice-Hall, Inc. Upper Saddle River, NJ Prentice Hall books are widely used by corporations and government agencies for training, marketing, and resale. The publisher offers discounts on this book when ordered in bulk quantities. For more information, contact: Corporate Sales Department, Phone: ; Fax: ; corpsales@prenhall.com; or write: Prentice Hall PTR, Corp. Sales Dept., One Lake Street, Upper Saddle River, NJ All products or services mentioned in this book are the trademarks or service marks of their respective companies or organizations. All rights reserved. No part of this book may be reproduced, in any form or by any means, without permission in writing from the publisher. Printed in the United States of America ISBN Prentice-Hall International (UK) Limited, London Prentice-Hall of Australia Pty. Limited, Sydney Prentice-Hall Canada Inc., Toronto Prentice-Hall Hispanoamericana, S.A., Mexico Prentice-Hall of India Private Limited, New Delhi Prentice-Hall of Japan, Inc., Tokyo Pearson Education Asia Pte. Ltd. Editora Prentice-Hall do Brasil, Ltda., Rio de Janeiro

5 ACKNOWLEDGMENTS ACKNOWLEDGMENTS FROM BEN ROSENZWEIG I would like to thank my co-author Elena Silvestrova for being a wonderful and knowledgeable colleague to work with. I would also like to thank Douglas Scherer for giving me the opportunity to work on this book as well as providing constant support and assistance through the entire writing process. I am indebted to Carol Brennan for her technical edits, she saved me from errors in every chapter. Finally I would like to thank the many friends and family, especially Edward Clarin and Edward Knopping, for helping me through the long process of putting the whole book together, which included many late nights and weekends. ACKNOWLEDGMENTS FROM ELENA SILVESTROVA My contribution to this book reflects the help and advice of many people. I am particularly indebted to the people at Prentice Hall who diligently worked to bring this book to market. Thanks to all of my students at Columbia University, who perennially demonstrated that teaching is learning. Thanks to Carol Brennan for her valuable comments and suggestions. To Ben Rosenzweig and Douglas Scherer, thanks for making this project a rewarding and enjoyable experience. Special thanks to David Dawson, whose insightful ideas and sincere support encourage me to work hard to the very end. Most importantly, thanks to my mom and dad, Natalia and Victor, whose excitement, enthusiasm, inspiration, and support were exceeded only by their love. xi

6 FROM THE EDITOR Prentice Hall s Interactive Workbooks are designed to get you up and running fast, with just the information you need, when you need it. We are certain that you will find our unique approach to learning simple and straightforward. Every chapter of every Interactive Workbook begins with a list of clearly defined Learning Objectives. A series of labs make up the heart of each chapter. Each lab is designed to teach you specific skills in the form of exercises. You perform these exercises at your computer and answer pointed questions about what you observe. Your answers will lead to further discussion and exploration. Each lab then ends with multiple-choice Self-Review Questions, to reinforce what you ve learned. Finally, we have included Test Your Thinking projects at the end of each chapter. These projects challenge you to synthesize all of the skills you ve acquired in the chapter. Our goal is to make learning engaging, and to make you a more productive learner. And you are not alone. Each book is integrated with its own Companion Website. The website is a place where you can find more detailed information about the concepts discussed in the Workbook, additional Self- Review Questions to further refine your understanding of the material, and perhaps most importantly, where you can find a community of other Interactive Workbook users working to acquire the same set of skills that you are. All of the Companion Websites for our Interactive Workbooks can be found at Timothy C. Moore VP, Executive Editor Pearson PTR Interactive xiii

7 INTRODUCTION The Oracle Interactive Workbook: PL/SQL presents the Oracle PL/SQL programming language in a unique and highly effective format. It challenges you to learn Oracle PL/SQL by using it rather than by simply reading about it. Just as a grammar workbook would teach you about nouns and verbs by first showing you examples and then asking you to write sentences, the Oracle PL/SQL workbook teaches you about cursors, procedures, and triggers by first showing you examples, and then asking you to create these objects yourself. WHO THIS BOOK IS FOR This book is intended for anyone who needs a quick but detailed introduction to programming with Oracle's PL/SQL language. The ideal readers are those with some experience with relational databases, with some Oracle experience, specifically with SQL and SQL*Plus, but with little or no experience with PL/SQL, or with most other programming languages. The content of this book is based on the material that is taught in an Introduction to PL/SQL class at Columbia University's CTA program New York City. The student body is rather diverse, in that there are some students who have years of experience with IT and programming, but no experience with Oracle PL/SQL, and then there are those with absolutely no experience in IT or programming. The content of the book, like the class, is balanced to meet the needs of both extremes. HOW THIS BOOK IS ORGANIZED The intent of this workbook is to teach you about Oracle PL/SQL by presenting you with a series of challenges followed by detailed solutions to those challenges. The basic structure of each chapter is as follows: xv

8 xvi Introduction Chapter Lab Exercises Exercise Answers with Detailed Discussion Self-Review Questions Lab... Test Your Thinking Questions Each chapter contains interactive Labs that introduce topics about Oracle PL/SQL. The topics are discussed briefly and then explored through exercises, which are the heart of each Lab. Each Exercise consists of a series of steps that you will follow to perform a specific task, along with questions that are designed to help you discover the important things about PL/SQL programming on your own. The answers to these questions are given at the end of the Exercises, along with more in-depth discussion of the concepts explored. The Exercises are not meant to be closed book quizzes to test your knowledge. On the contrary, they are intended to act as your guide and walk you through a task. So, you are encouraged to flip back and forth from the Exercise question section to the Exercise answer section so that, if need be, you can read the answers and discussions as you go along. At the end of each Lab is a series of multiple-choice Self-Review Questions. These are meant to be closed book quizzes to test that you have the Lab material. The answers to these questions appear in Appendix A. There are also additional Self-Review Questions at this book s companion Web site, found at Finally, at the end of each chapter you will find a Test Your Thinking section, which consists of a series of projects designed to solidify all of the skills you have learned in the chapter. If you have successfully completed all of the Labs in the chapter, you should be able to tackle these projects with few problems. You will find guidance and/or solutions to these at the companion Web site. The chapters should be completed in sequence because PL/SQL builds itself chapter by chapter. Additionally, many of the files you create and save in earlier chapters will be required in later chapters. In the end, all of the skills you have acquired, and files you have created, will come together in Chapter 13 and 14, Packages and Stored Code, where you will create a package.

9 Introduction xvii ABOUT THE COMPANION WEB SITE The companion Web site is located at Here you will find two very important things: 1) Files you will need before you begin reading the workbook. 2) Answers to the Test Your Thinking questions. All of the Exercises and questions are based on a sample database called STUDENT. The files required to created and install this STUDENT schema are downloadable from the Web site. The answers to the Test Your Thinking section will also be found at the web site. In addition to required files and Test Your Thinking answers, the Web site will have many other features like additional review questions, a message board, and periodically updated information about the book. You should visit the companion Web site and download the required files before starting the Labs and Exercises. WHAT YOU LL NEED There are software programs as well as knowledge requirements necessary to complete the exercise sections of the workbook. SOFTWARE Oracle8 SQL*Plus Access to the WWW Windows 95/98 or NT 4.0

10 xviii ORACLE8 Introduction Oracle8 is Oracle's RDBMS and its flagship product. You can use either Oracle Personal Edition or Oracle Enterprise Edition. If you use Oracle Enterprise Edition, this can be running on a remote server or locally on your own machine. Oracle Enterprise Edition running locally was used to create the exercises for this book but subsequent versions should be compatible (the web site will also have scripts to create a database that will function for Oracle 7.3 and above). Additionally, you should have access to and be familiar with SQL*Plus. This book was used running SQL*Plus version You have a number of options for how to edit and run scripts from SQL*Plus. There are also many third-party programs to edit and debug PL/SQL. SQL*Plus is used throughout this book, since SQL*Plus comes with the Oracle Personal Edition and Enterprise Edition. SQL*PLUS You should be familiar with using SQL*Plus to execute SQL statements (if not then refer to the other book in the Prentice Hall Interactive Oracle Series on this topic Morrison/Rishchert's Oracle Interactive Workbook: SQL). There are a few key differences between executing SQL statement in SQL*Plus and executing PL/SQL statements in SQL*Plus. You will be introduced to these differences so that you can work with the exercises in this book. You can end an SQL Command in SQL*Plus in one of three ways: 1) with a semicolon (;) 2) with a backslash (/) on a line by itself or 3) with a blank line. The semicolon (;) tells SQL*Plus that you want to run the command that you have just entered. You type the semicolon at the end of the SELECT statement and then press return. SQL*Plus will process what is in the SQL Buffer. FOR EXAMPLE SQL> select sysdate 2 from dual 3 ; SYSDATE

11 Introduction xix 24-NOV-99 SQL> THE SQL BUFFER SQL*Plus will store the SQL command or PL/SQL block that you have most recently entered in an area of memory known as the SQL Buffer. The SQL Buffer will remain unchanged until you enter a new command or exit your SQL*Plus session. You can easily edit the contents of the SQL Buffer by typing EDIT at the SQL prompt. The default text editor will open with the contents of the SQL Buffer. You can edit the file and then exit the editor. This will cause the contents of the SQL Buffer to change. SQL*Plus commands such as SET SERVEROUTPUT ON are not captured into the SQL Buffer nor does SQL*Plus store the semicolon or the slash you type to execute a command in the SQL buffer. When you create stored procedures, functions or packages you begin with the CREATE command. When you begin a PL/SQL block, you start by entering the word DECLARE or BEGIN. Typing either BEGIN, DECLARE or CREATE will put the SQL*Plus session into PL/SQL mode. RUNNING PL/SQL BLOCKS IN SQL*PLUS Once you are in PL/SQL mode, you will not be able to end the block in the same manner that you ended a SQL block. The semicolon (;) can be used multiple times in a single PL/SQL subprogram, thus when you end a line with a semicolon you will not terminate the PL/SQL subprogram. You can terminate the PL/SQL subprogram by entering a period(.). This will end the block and leave the block in the SQL Buffer, but it will not execute the subprogram. You have a choice, to enter EDIT and edit the program, or execute the subprogram with a backslash (/) or an RUN. A semicolon (;) will not execute these SQL commands as it does other SQL commands. You might enter and execute a PL/SQL subprogram as follows: SQL> BEGIN 2 DBMS_OUTPUT.PUT_LINE('This is a PL/SQL Block'); 3 END; 4. SQL> /

12 xx Introduction This is a PL/SQL Block PL/SQL procedure successfully completed. SQL> If you run a script file that you have saved on your computer, you must remember to complete your program with a period(.). If you simply want to put the code into the SQL Buffer you can end the script with a backslash (/) which will execute the file. The failure to end your PL/SQL block with a period (.) or a backslash (/) will prevent your block from executing. WINDOWS 95/98 OR NT 4.0 The SQL*Plus development environment is available on a number of different operating system platforms including Microsoft Windows and various flavors of UNIX. The exercises and examples in this workbook were created using Microsoft Windows NT 4.0 with service pack 3. Therefore, they are geared more for those working in a Windows environment. But, as mentioned before, most of the concepts in this book are rather fundamental and, therefore, apply to all operating systems. So, even if you are developing on a UNIX platform, this book can still be of use to you. ABOUT THE SAMPLE SCHEMA The STUDENT schema contains tables and other objects meant to keep information about a registration and enrollment system for a fictitious university. There are ten tables in the system that store data about students, courses, instructors and so on. In addition to storing contact information (address and telephone number) for students and instructors, and descriptive information about courses (COST and PREREQUISITES), the schema also keeps track of the sections for particular courses, and the sections in which students have enrolled. The SECTION and ENROLLMENT tables are two of the most important tables in the schema. The SECTION table stores data about the individual sections that have been created for each course. Each section record also

13 Introduction xxi stores information about where and when the section will meet, and which instructor will teach the section. The section table is related to the course table and the instructor table. The enrollment table is equally important, because it keeps track of which students have enrolled in which sections. Each enrollment record also stores information about the student's grade and enrollment date. The enrollment table is related to the student table and the section table. The schema also has a number of other tables that manage grading for each student in each section. CONVENTIONS USED IN THIS BOOK There are several conventions that are used in this book to try and make your learning experience easier. These are explained here. This icon is used to flag notes or advice from the author to you, the reader. For instance, if there is a particular topic or concept that you really need to understand for the exam, or if there s something that you need to keep in mind while working, you will find it set off from the main text like this. This icon is used to flag tips or especially helpful tricks that will save you time or trouble. For instance, if there is a shortcut for performing a particular task or a method that the author has found useful, you will find it set off from the main text like this. Computers are delicate creatures and can be easily damaged. Likewise, they can be dangerous to work on if you re not careful. This icon is used to flag information and precautions that will not only save you headaches in the long run, they may even save you or your computer from harm. This icon is used to flag passages with a reference to the book s companion Web site, which once again is located at:

14 Oracle PL/SQL INTERACTIVE WORKBOOK