Writing efficient SQL queries

You might be able to rewrite certain SQL statements to enable more efficient access path selection.

Before you begin

Tip: Query tuning capabilities that can help you with this task, such as visual explain and statistics advisor, are available in IBM® Db2 Administration Foundation for z/OS® and IBM Db2 for z/OS Developer Extension.

Before rewriting existing SQL statements in response to performance problems, check the organization of the data and the availability and accuracy of the data statistics. For more information, see Monitoring catalog statistics.