So the CASE... WHEN solution posted previously works very well for MySQL. Lots of nice views popping up and databases going forward.

However, when attempting to link a view as a table in Microsoft Access the calculated columns won't show. It's a real drag as it is such quick work to use views to de-normalize data for backwards compatibility.

Enter the pass-through query which solves this problem as long as having the data in an Access query is suitable.