Introduction to SQL: Mastering the Relational Database Language, Fourth Edition/20th Anniversary Edition

Chapter 20. Using Indexes

Introduction

Some SQL statements have a reasonably constant execution time. Examples include the CREATE TABLE and GRANT statements. It does not matter under which circumstances such statements are executed; they always need a certain execution time. There is no way to reduce their execution time. However, this is not the case for all statements. The time required to process SELECT, UPDATE, and DELETE statements varies from one statement to the next. One SELECT statement might be processed in 2 seconds, while another could take minutes. The required execution time of this type of statements can indeed be influenced.

Many techniques are available for reducing the execution time of SELECT, UPDATE, and DELETE statements. These ...