Evaluating SARG and Join Selectivity
To determine selectivity of a SARG, which helps in determining the most efficient query plan, the Cardinality Estimator uses the statistical information stored for the index or column, if any. If no statistics are available for a column or index, SQL Server will automatically create statistics on nonindexed columns specified in a SARG if the AUTO_CREATE_STATISTICS option is enabled for the database. SQL Server also automatically generates and updates the statistics for any indexed columns referenced in a SARG if the AUTO_UPDATE_STATISTICS option is enabled. In addition, you can explicitly create statistics for a column or set of columns in a table or an indexed view by using the CREATE STATISTICS command. ...
Get Microsoft SQL Server 2014 Unleashed now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
