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Computes the average of the independent variable of the regression line.
REGR_AVGX( dependent-expression , independent-expression )
REGR_AVGX( dependent-expression , independent-expression ) OVER ( window-spec )
window-spec : see Syntax 2 instructions in the Remarks 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 y represents the independent-expression:
AVG( y )
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.
SQL/2003 SQL foundation feature (T621) outside of core SQL.
The following example calculates the average of the dependent variable, employee age.
SELECT REGR_AVGX( Salary, ( YEAR( NOW() ) - YEAR( BirthDate ) ) ) FROM Employees;
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