This function converts its arguments to DOUBLE, and performs the computation in double-precision floating-point arithmetic.
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 dependent-expression and x represents the independent-expression:
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 with a WINDOW clause in the SELECT statement. See the window-spec definition for the WINDOW clause.
For more information about using window functions in SELECT statements, including working examples, see Window functions.