Preface

A poorly performing database application can cost each user time and have an impact on other applications running on the same computer or the same network.

The purpose of this book is to help you improve the performance of your SQL database. It is not an introduction to SQL syntax, not a tuning manual for a specific SQL implementation, and not a guide to design or data modelling. Instead, we've written it for users and programmers who want to improve SQL performance, no matter what brand of SQL they use. In this book, you'll find tuning tips for common situations, such as, "How to change a query so it will go faster," "What an index does," and "Shifting work from the server to the client."

Rather than exploiting the unique features of a single DBMS, we're going to give you ideas that are good for all of the major SQL DBMSs. Client/server programmers and consultants need to appreciate what can happen when the DBMS changes, orthe most challenging situationthe DBMS is unknown. So we tested all the ideas in this book on eight well-known DBMSs.

A good DBMS already contains a good optimizer. Yet you have picked up a book that promises to help you do your own tuning. That means that either you don't know something or you do know something.

• You don't know that your DBMS is good.

• You know that even good tools work better in skilled hands.