Returns the sum of squares of the independent expressions used in a linear regression model. The REGR_SXX function can be used to evaluate the statistical validity of a regression model.

**REGR_SXX(** *dependent-expression* ,* independent-expression*** )**

**REGR_SXX(** *dependent-expression* ,* independent-expression*** ) OVER (**

*window-spec* : see Syntax 2 instructions in the Usage section below

**dependent-expression** The variable that is affected by the independent variable.

**independent-expression** The variable that influences the outcome.

This function converts its arguments to DOUBLE, performs the computation in double-precision floating point, and returns a DOUBLE as the result. If the function is applied to an empty set, then it returns NULL.

The function is applied to the set of (*dependent-expression* and *independent-expression*) pairs after eliminating all pairs for which either *dependent-expression* or *independent-expression* is NULL. The function is computed simultaneously during a single pass through the data. After eliminating NULL values, the following computation is then made, where *x* represents the *dependent-expression* and *y* represents the *independent-expression*:

REGR_COUNT(x,y) * VAR_POP(x)

For more information about the statistical computation performed, see Mathematical formulas for the aggregate functions.

Syntax 2 represents usage as a window function in a SELECT statement. As such, elements of *window-spec* can be specified either in the function syntax (inline), or in conjunction with a WINDOW clause in the SELECT statement. See the *window-spec* definition provided in WINDOW clause.

For more information about using window functions in SELECT statements, including working examples, see Window functions.

- REGR_COUNT function [Aggregate]
- REGR_INTERCEPT function [Aggregate]
- REGR_COUNT function [Aggregate]
- REGR_AVGX function [Aggregate]
- REGR_AVGY function [Aggregate]
- REGR_SXY function [Aggregate]
- REGR_SYY function [Aggregate]
- VAR_POP function [Aggregate]

**SQL/2003**SQL foundation feature (T621) outside of core SQL.

The following example returns the value 5916.4800000000105.

SELECT REGR_SXX( Salary, ( YEAR( NOW() ) - YEAR( BirthDate ) ) ) FROM Employees;