John Mitchell-245523 (7/18/2013)
(3) The statistics update automatically triggered by ALTER INDEX REBUILD is based on a limited scan of the data, whereas UPDATE STATISTICS is based on a full scan.
Other way around.
When an index rebuild is run, the statistics on that index are updated with fullscan as part of the index rebuild process. It's not that the rebuild is triggering an automatic update, it's not. The update is part and parcel of the index rebuild operation.
On larger tables, UPDATE STATISTICS is sampled unless WITH FULLSCAN is specified. The details of what constitutes large and the sample rates are detailed in Books Online.
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