MySQL Reference Manual - 4.0.20

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19. Stored Procedures and Functions

Stored procedures and functions are a new feature in MySQL version 5.0. A stored procedure is a set of SQL statements that can be stored in the server. Once this has been done, clients don't need to keep reissuing the individual statements but can refer to the stored procedure instead.

Stored procedures can provide improved performance because less information needs to be sent between the server and the client. The tradeoff is that this does increase the load on the database server system because more of the work is done on the server side and less is done on the client (application) side. And, often, there are multiple client machines (such as Web servers) but only one or a few database servers.

Stored procedures also allow you to have libraries of functions in the database server. However, modern application languages already allow such design internally with, for example, classes. Using these client application language features is beneficial for the programmer even outside the scope of database use.

Some situations where stored procedures can be particularly useful:

When multiple client applications are written in different languages or work on different platforms, but need to perform the same database operations.
When security is paramount. Banks, for example, use stored procedures for all common operations. This provides a consistent and secure environment, and procedures can ensure that each operation is properly logged. In such a setup, applications and users would not get any access to the database tables directly, but can only execute specific stored procedures.

MySQL follows the SQL:2003 syntax for stored procedures, which is also used by IBM's DB2.

The MySQL implementation of stored procedures is still in progress. All syntax described in this chapter is supported and any limitations and extensions are documented where appropriate.

Stored procedures require the proc table in the mysql database. This table is created during the MySQL 5.0 installation procedure. If you are upgrading to MySQL 5.0 from an earlier version, be sure to update your grant tables to make sure that the proc table exists. See section Upgrading the Grant Tables.