Running Sum: RSUM

Use RSUM to traverse the current result set to do running sum window based calculations. For example, the following RSUM formula requires a window size and calculates the trailing sum of values at the current report grain for the window provided.

RSUM(window_size_integer, [measure])

For example, using Northwind data, show the running sum for different values of last N, showing that N is just the same as the measure itself.