Using Computed Columns to Avoid Scans without Changing Queries

Andy Mallon shares a trick you don’t want to use too often, but can get you out of a pinch:

We’ve all been there. You’ve got a query where the JOIN or WHERE predicate is not SARGable. You’ve read about how this can be a problem, and how bad it is for performance.

Alas, you cannot change the query. Sometimes this reason is political, sometimes it’s because you’ve got a third-party app and simply don’t have access to the code. But you do have access to the database…

This is the type of thing you learn about and use maybe twice in your career, and then you get frustrated with the third-party vendor which won’t fix their code.