SAS Certification Prep Guide, 4th Edition

Using an Index for Efficient WHERE Processing

Overview

When processing a WHERE expression, SAS determines which of the following access methods is likely to be most efficient:

	SAS examines all observations sequentially in their physical order.
	SAS uses an index to access specific observations directly. Using an index to process a WHERE expression is referred to as optimizing the WHERE expression.

Using an index to process a WHERE expression improves performance in some situations but not in others. For example, it is more efficient ...