I'm not a db-engine expert, but if I'd have to write this functionality myself, I'd perform the computation only when any of the involved columns change, not on

I'm not a db-engine expert, but if I'd have to write this functionality myself, I'd perform the computation only when any of the involved columns change, not on every read. EDIT: sorry, I read your comment on the opposite way. I see we are saying the exact same thing :)