Friday, July 2, 2010

Rebuilding Indexes vs Updating Statistics

No matter in which order you perform these, here are some points to keep in mind

 

1) By default, the UPDATE STATISTICS statement uses only a sample of records of the table. Using UPDATE STATISTICS WITH FULLSCAN will scan the entire table.

2) By default, the UPDATE STATISTICS statement updates both index and column statistics. Using the COLUMNS option will update column statistics only. Using the INDEX option will update index statistics only.

3) Rebuilding an index, for example by using ALTER INDEX … REBUILD, will also update index statistics with the equivalent of using WITH FULLSCAN. Rebuilding indexes does not update column statistics.

4) Reorganizing an index, for example using ALTER INDEX … REORGANIZE, does not update any statistics.

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