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ESTIMATE function [Miscellaneous]

Provides selectivity estimates for the query optimizer, based on specified parameters.

ESTIMATE( column-name [, value [, relation-string ] ] )

column-name    The column used in the estimate.

value    The value to which the column is compared. The default is NULL.

relation-string    The comparison operator used for the comparison, enclosed in single quotes. Possible values for this parameter are: =, >, <, >= , <=, <>, !=, !<, and !>. The default is =.

If value is NULL then the relation strings '=' and '!=' are interpreted as the IS NULL and IS NOT NULL conditions, respectively.

• INDEX_ESTIMATE function [Miscellaneous]
• ESTIMATE_SOURCE function [Miscellaneous]

• SQL/2003    Vendor extension.

The following statement returns the percentage of EmployeeID values estimated to be greater than 200. The precise value depends on the actions you have carried out on the database.

SELECT FIRST ESTIMATE( EmployeeID, 200, '>' )
   FROM Employees;