What is UPDATE STATISTICS ?
SQL Server keeps statistics about the distribution of the key values in each index and uses these statistics to determine which index(es) to use in query processing. Users can create statistics on nonindexed columns by using the CREATE STATISTICS statement.
Query optimization depends on the accuracy of the distribution steps:
- If there is significant change in the key values in the index, rerun UPDATE STATISTICS on that index.
- If a large amount of data in an indexed column has been added, changed, or removed (that is, if the distribution of key values has changed), or the table has been truncated using the TRUNCATE TABLE statement and then repopulated, use UPDATE STATISTICS.
Statistics can be created or updated on tables with computed columns only if the conditions are such that an index can be created on these columns.