SAS Certification Prep Guide, 4th Edition

Identifying Available Indexes

Overview

The first step for SAS is to determine whether there are any existing indexes that might be used to process the WHERE expression. Specifically, SAS checks the variable in each condition in the WHERE expression to determine whether the variable is a key variable in an index.

SAS can use either a simple index or a composite index to optimize a WHERE expression. To be considered for use in optimizing a single WHERE condition, one of the following requirements must be met:

• the variable in the WHERE condition is the key variable in a simple index
• the variable in the WHERE condition is the first key ...