Never would have thought to solve this kind of problem this way. Superb solution! 🙂

Totally agree here. But what would happen if we take out the GETUTCDATE() into a variable and change the call of DATEDIFF with it? What would be the impact?

Great job, much appreciated!. Although, a small correction to your script.
In the first part, with @BirthDate and @Today declared as DATETIME, the TallyGenerator for years should be called starting...

Useful tsql found in 70-431 documentation and modified to meet my needs.

SELECT

OrderId

, SiteId

, ClientId

, DocumentDate

, TotalAmount

, SUM(TotalAmount) OVER(PARTITION BY ClientId

ORDER BY DocumentDate, OrderId, SiteId

ROWS BETWEEN UNBOUNDED PRECEDING

AND...