Book Image

IBM DB2 9.7 Advanced Application Developer Cookbook

Book Image

IBM DB2 9.7 Advanced Application Developer Cookbook

Overview of this book

With lots of new features, DB2 9.7 delivers one the best relational database systems in the market. DB2 pureXML optimizes Web 2.0 and SOA applications. DB2 LUW database software offers industry leading performance, scale, and reliability on your choice of platform on various Linux distributions, leading Unix Systems like AIX, HP-UX and Solaris and MS Windows platforms. This DB2 9.7 Advanced Application Developer Cookbook will provide an in-depth quick reference during any application's design and development. This practical cookbook focuses on advanced application development areas that include performance tips and the most useful DB2 features that help in designing high quality applications. This book dives deep into tips and tricks for optimized application performance. With this book you will learn how to use various DB2 features in database applications in an interactive way.
Table of Contents (15 chapters)
IBM DB2 9.7 Advanced Application Developer Cookbook
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface

Using ROWNUM and DUAL in DB2 9.7


The ROWNUM and DUAL supports are enabled by setting the DB2_COMPATIBILITY_VECTOR registry variable to ORA.

Oracle programmers use ROWNUM quite often to retrieve a controlled number of rows from a SQL statement. The same can be applied in DB2 9.7.

Getting ready

Enable the compatibility feature by setting the DB2_COMPATIBILITY_VECTOR registry to ORA.

How to do it...

In earlier versions of DB2, when we wanted to return only a specific number of rows of an SQL statement, we used the FETCH FIRST clause. Now that we have the Oracle compatibility feature enabled in DB2 9.7, we can use ROWNUM as in Oracle. In DB2, ROWNUM supports<, >, >=, <=, =, and BETWEEN operators.

We can combine ROWID and ROWNUM together to display the physical address of the row in the database. This value is a unique identifier of the row, and does not change over until a REORG occurs on the table.

Let's start using the ROWNUM on the existing sample database tables. With ROWNUM...