Now, you have looked at a variety of ways to improve the performance of database queries in your PHP applications. Since the usual performance bottleneck is the reading of large quantities of data, the focus of this section was on database reads or SELECTs. However, you can apply many of the same concepts to alleviate any performance bottlenecks associated with database updates.

In addition to reviewing the SQL statements used to extract data, you should also be conscious of performance issues that may have been introduced by how you retrieved the result sets.

In Other performance enhancements, I go on to look at more drastic ways to improve the performance of your Web application.