Whats New for Statistics in SQL Server 2005?
SQL Server 2005 has a number of new statistics features that allow the query optimizer to choose better query plans for a broader range of queries, or otherwise improve the management of statistics. These include the following enhancements: • String summary statistics: Information about the frequency distribution of substrings is maintained for character columns. This helps the optimizer better estimate the selectivity of conditions that use the LIKE operator. • Asynchronous auto update statistics: The ALTER DATABASE option AUTO_UPDATE_STATISTICS_ASYNC is new in SQL Server 2005. The option is off by default. When enabled, this option causes SQL Server 2005 to perform automatic update of statistics in the background. The query that caused the statistics update does not block. It proceeds with the old statistics. This provides more predictable query response time for some work loads. • Computed column statistics: Statistics can be manually or automatically created and updated on computed
