By now, you should have a good understanding of the importance of indexes. It is equally important for the optimizer to have the necessary statistics on the data distribution so that it can choose indexes effectively. In SQL Server, this information is maintained in the form of statistics on the index key.
In this chapter, you'll learn the importance of statistics in query optimization. Specifically, I cover the following topics:
The role of statistics in query optimization
The importance of statistics on columns with indexes
The importance of statistics on nonindexed columns used in join and filter criteria
Analysis of single-column and multicolumn statistics, including the computation of selectivity of a column for ...