STATS_DATE (Transact-SQL)

Άρθρο
05/23/2023

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance Azure Synapse Analytics Analytics Platform System (PDW) SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

Returns the date of the most recent update for statistics on a table or indexed view.

For more information about updating statistics, see Statistics.

Transact-SQL syntax conventions

Syntax

STATS_DATE ( object_id , stats_id )

Arguments

object_id
ID of the table or indexed view with the statistics.

stats_id
ID of the statistics object.

Return Types

Returns datetime on success. Returns NULL if a statistics blob was not created.

Remarks

System functions can be used in the select list, in the WHERE clause, and anywhere an expression can be used.

Statistics update date is stored in the statistics blob object together with the histogram and density vector, not in the metadata. When no data is read to generate statistics data, the statistics blob is not created, and the date is not available. This is the case for filtered statistics for which the predicate does not return any rows, or for new empty tables.

If statistics correspond to an index, the stats_id value in the sys.stats catalog view is the same as the index_id value in the sys.indexes catalog view.

Permissions

Requires membership in the db_owner fixed database role or permission to view the metadata for the table or indexed view.

Examples

A. Return the dates of the most recent statistics for a table

The following example returns the date of the most recent update for each statistics object on the Person.Address table.

USE AdventureWorks2022;  
GO  
SELECT name AS stats_name,   
    STATS_DATE(object_id, stats_id) AS statistics_update_date  
FROM sys.stats   
WHERE object_id = OBJECT_ID('Person.Address');  
GO

If statistics correspond to an index, the stats_id value in the sys.stats catalog view is the same as the index_id value in the sys.indexes catalog view, and the following query returns the same results as the preceding query. If statistics do not correspond to an index, they are in the sys.stats results but not in the sys.indexes results.

USE AdventureWorks2022;  
GO  
SELECT name AS index_name,   
    STATS_DATE(object_id, index_id) AS statistics_update_date  
FROM sys.indexes   
WHERE object_id = OBJECT_ID('Person.Address');  
GO

Examples: Azure Synapse Analytics and Analytics Platform System (PDW)

B. Learn when a named statistics was last updated

The following example creates statistics on the LastName column of the DimCustomer table. It then runs a query to show the date of the statistics. Then it udpates the statistics and runs the query again to show the updated date.

--First, create a statistics object  
USE AdventureWorksPDW2012;  
GO  
CREATE STATISTICS Customer_LastName_Stats  
ON AdventureWorksPDW2012.dbo.DimCustomer (LastName)  
WITH SAMPLE 50 PERCENT;  
GO  
  
--Return the date when Customer_LastName_Stats was last updated  
USE AdventureWorksPDW2012;  
GO  
SELECT stats_id, name AS stats_name,   
    STATS_DATE(object_id, stats_id) AS statistics_date  
FROM sys.stats s  
WHERE s.object_id = OBJECT_ID('dbo.DimCustomer')  
    AND s.name = 'Customer_LastName_Stats';  
GO  
  
--Update Customer_LastName_Stats so it will have a different timestamp in the next query  
GO  
UPDATE STATISTICS dbo.dimCustomer (Customer_LastName_Stats);  
  
--Return the date when Customer_LastName_Stats was last updated.  
SELECT stats_id, name AS stats_name,   
    STATS_DATE(object_id, stats_id) AS statistics_date  
FROM sys.stats s  
WHERE s.object_id = OBJECT_ID('dbo.DimCustomer')  
    AND s.name = 'Customer_LastName_Stats';  
GO

C. View the date of the last update for all statistics on a table

This example returns the date for when each statistics object on the DimCustomer table was last updated.

--Return the dates all statistics on the table were last updated.  
SELECT stats_id, name AS stats_name,   
    STATS_DATE(object_id, stats_id) AS statistics_date  
FROM sys.stats s  
WHERE s.object_id = OBJECT_ID('dbo.DimCustomer');  
GO

USE AdventureWorksPDW2012;  
GO  
SELECT name AS index_name,   
    STATS_DATE(object_id, index_id) AS statistics_update_date  
FROM sys.indexes   
WHERE object_id = OBJECT_ID('dbo.DimCustomer');  
GO

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