Code 'Running Totals' to run 100s to 1000s times Faster using Window Function - Hands On Easy Demo!

If you have to perform an TSQL operation against a large number of rows in a table using a running total , you need to code it in the most performant way possible. Using a TSQL Window Function is your best friend and may show performance improvement 100s to 1000s of times faster than some more obvious methods. In some cases adding a Columnstore index (even a fake) with a Window Function can even add another level of magnitude to this already mind blowing performance. Wow!

I will go through three sizes of table and demonstrate the code and query plans that show this astounding differences.

[marshalljackson]

Very helpful explanation and useful to compare the "slow" way vs Windows Functions