Sql updating statistics

Posted by / 05-Nov-2017 10:51

Sql updating statistics

By default, the query optimizer already updates statistics as necessary to improve the query plan; in some cases you can improve query performance by using UPDATE STATISTICS or the stored procedure sp_updatestats to update statistics more frequently than the default updates.Transact-SQL Syntax Conventions is not specified, the query optimizer updates all statistics for the table or indexed view.It is therefore important to appreciate how SQL Server maintains distribution statistics.As part of our ongoing discussions comparing SQL Server to Oracle, Jonathan Lewis and I are going to be talking about statistics next.Each statistics object contains a histogram displaying the distribution of values of the column (or of the first column in the case of multi-column statistics).Multi-column statistics also contains a correlation of values among the columns (called ), which are derived from the number of distinct rows or the column values.

For more information about AUTO_CREATE_STATISTICS, see can be from 0 to the total number of rows.Statistics contain two different types of information about the data; density and distribution.Density is simply the inverse of the count of distinct values for the column or columns.You can update query optimization statistics on a table or indexed view in SQL Server 2017 by using SQL Server Management Studio or Transact-SQL.By default, the query optimizer already updates statistics as necessary to improve the query plan; in some cases you can improve query performance by using UPDATE STATISTICS or the stored procedure to update statistics more frequently than the default updates.

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Statistics refers to the statistical information about the distribution of values in one or more columns of a table or an index.

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