Don't you mean it's rare for LHS to be a constant in SQL statements. Or is the problem that 'rare in most' as opposed to just saying 'rare' can be satisfied by a 51% hit rate (most can be 50.5%, with rare being say 1.5% inside that, but by saying nothing about the other 49.5% allows them all to be hits). One has to be rigorous with verbal expression of statistical propositions.