One of my favorite SQL Server topics to teach about is the query optimizer, whose job is to determine which query plans SQL Server will use to execute the queries your applications submit for processing. A main optimizer task is to determine which indexes, if any, SQL Server will use to find the relevant data in each table involved in a query. In my July 2001 column, "Are You in Tune?" (InstantDoc ID 21038), I introduced the concept of a SARG, which is my term for a particular form of search argument condition in a query's WHERE clause. In most cases, a column must appear in a SARG before the query optimizer will consider using an index on that column.

A S...