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.