Microsoft® SQL Server 2008 R2 Unleashed

Identifying Search Arguments

A SARG is defined as a WHERE clause that compares a column to a constant. The format of a SARG is as follows:

Column operator constant_expression [and...]

SARGs provide a way for the Query Optimizer to limit the rows searched to satisfy a query. The general goal is to match a SARG with an index to avoid a table scan. Valid operators for a SARG are =, >, <, >=, and <=, BETWEEN, and LIKE. Multiple SARGs can be combined with the AND clause. (A single index might match some or all of the SARGs ANDed together.) Following are examples of SARGs:

• flag = 7

• salary > 100000

• city = 'Saratoga' and state = 'NY'

• price between $10 and $20 (the same as price > = $10 and price <= $20)

• 100 between lo_val and hi_val (the same ...