Hi there,
A subquery as I know it is part of the where clause. A simple example:
As might be obvious most, if not all, subqueries can be reformulated to be simply joins (rather obvious in this example). That is also what a decent optimizer would do.
Subqueries do have a use in keeping your SQL readable, certainly when the statements get more complex, I 'd say.
Good riddance,
Rudy.