Most Web applications of any size involve the use of a database. Typically, a Web application allows the addition or creation of new records (for example, when a new user registers on the site), and the reading and searching of many records in a database. The most common bottleneck when developing a Web application is in the reading of a large number of records from a database, or executing a particularly complex SELECT statement against the database.

Writing to or updating a database usually is performed on a small number of records at a time. This is often much less of an issue than cases that involve reading thousands of records at a time. Consequently, in this section, I look at different ways to speed up your database queries (also known as reads). Many of the same techniques can be applied to database updates (also known as writes).

Finally, since I'm looking at ways to write more efficient SQL statements, the techniques presented here are independent of the underlying database engine. Obviously, you will obtain different performance improvements with different database engines, as well as different database schema.