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However, in SQL Server 2012 we can look at the plan XML and confirm this.
In his post, Statistics used in a cached query plan, Fabiano Neves Amorim describes a method to capture statistics information from the plan.
To be clear, if a query plan exists in cache and that plan uses specific statistics, when the query executes SQL Server checks to see if any of the statistics used in the plan are out of date.
If they are, then the automatic update of those statistics occurs.
Sales Order Detail IX_Sales Order Detail — Update one column on a table specifying sample size UPDATE STATISTICS Production.
Product(Products) WITH SAMPLE 50 PERCENT [/cc] Using update statistics can give you the granularity of control to only update the out of date statistics, thus having less impact on your production system.
This command gives much better granularity of control: [cc lang=”sql”] — Update all statistics on a table UPDATE STATISTICS Sales.
I just created the table, so the Last Updated date is current, and I have not made any changes so the modification count is 0.
I had many people ask why statistics did not update immediately after the bulk load of the 25,000 rows completed, so I want to step through the demo that I did at Summit to clarify when an automatic update will occur.
The Setup Start with a copy of the USE [Adventure Works2012]; GO SELECT * INTO [Sales].[Test Sales Order Detail] FROM [Sales].[Sales Order Detail]; GO CREATE CLUSTERED INDEX [PK_Sales Order Detail_Sales Order ID_Sales Order Detail ID] ON [Sales].[Test Sales Order Detail] ([Sales Order ID], [Sales Order Detail ID]); GO CREATE UNIQUE NONCLUSTERED INDEX [AK_Test Sales Order Detail_rowguid] ON [Sales].[Test Sales Order Detail] ([rowguid]); GO CREATE NONCLUSTERED INDEX [IX_Test Sales Order Detail_Product ID] ON [Sales].[Test Sales Order Detail] ([Product ID]); GO SELECT OBJECT_NAME([sp].[object_id]) AS "Table", [sp].[stats_id] AS "Statistic ID", [s].[name] AS "Statistic", [sp].[last_updated] AS "Last Updated", [sp].[rows], [sp].[rows_sampled], [sp].[unfiltered_rows], [sp].[modification_counter] AS "Modifications" FROM [sys].[stats] AS [s] OUTER APPLY sys.dm_db_stats_properties ([s].[object_id],[s].[stats_id]) AS [sp] WHERE [s].[object_id] = OBJECT_ID(N'Sales.
During the PASS Summit in November I presented a session on Demystifying Database Statistics (if you attended Summit but missed it, you can stream it from here).
During the session I went through a demo that showed the automatic update of a statistic.