SQL query tuning is an essential performance component.

 

Because query tuning specifics depend on the underlying database structure, this document cannot provide a comprehensive examination of query tuning. Your database documentation should contain specific query tuning information; there are also many third party books on SQL query tuning available for purchase.

 

Much of the specific database information on SQL query tuning is also applicable to CONNX. For example, the natural relationships between sort order and index selection can help you decide when and how to use an ORDER BY clause. And understanding the relationship between table cardinality, index selection, join order, and usage of various operators is essential to understand SQL query performance.

 

CONNX provides access to the query plan via the {statistics} function. Please refer to the CONNX User Guide for more information.