This is just denormalization. If you need to invalidate this "cache", it's extremely expensive to find the records that need updating. It's probably better to

This is just denormalization. If you need to invalidate this "cache", it's extremely expensive to find the records that need updating. It's probably better to use a summary table that's populated with triggers, or to just optimize your indexes and use a JOIN (the world won't end, I promise).