Yeah, correlated subqueries are fine. Unless you're on MySQL, which (historically, at least) was infamously terrible at executing them. The reason this query w

Yeah, correlated subqueries are fine. Unless you're on MySQL, which (historically, at least) was infamously terrible at executing them. The reason this query works is because correlated subqueries... need something to correlate with! Usually the column from the outside query is only referenced in the WHERE clause, but there isn't really a reason you can't reference it in the inside query's SELECT clause. After all, what if you needed it for a CASE expression there? There are certainly better ways to write what this query is accomplishing -- at the very least there are ways to write it that make it much more clear what your intentions are -- but just because it's weird doesn't mean it's invalid. The developers know they cannot anticipate all possible operations that might be desired, and there are already countless ways to write queries incorrectly.