This function is the same as the ESTIMATE function, except that it always looks only in an index.
INDEX_ESTIMATE( column-name, number
[ , relation-string ]
column-name The name of the column that is used in the estimate.
number If number is specified, the function returns as a REAL the percentage estimate that the query optimizer uses.
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.
SQL/2003 Vendor extension.
The following statement returns the value 89.4736862183.
SELECT FIRST ESTIMATE( EmployeeID, 200, '>' ) FROM Employees;