Hi,
> Now as expected it's an dependent subquery and makes use of the index on
> document_id. BUT: If we change the "SELECT id" in the subquery to
> "SELECT document_id" or "SELECT 1", we get:
>
> *** 1. row ***
> [...]
> **
Hi all,
the manual says:
"If a subquery returns any rows at all, then EXISTS subquery is TRUE,
and NOT EXISTS subquery is FALSE. ... Traditionally, an EXISTS subquery
starts with SELECT *, but it could begin with SELECT 5 or SELECT column1
or anything at all. MySQL ignores the SELECT list in such
