Subqueries Introduced with Comparison Operators and ANY or ALL
Another kind of subquery, which returns any number of rows (including none) for the outer query, uses a comparison operator modified with keywords ALL or ANY. Subqueries introduced with a modified comparison operator take the following general form:
Start of SELECT, INSERT, UPDATE, DELETE statement; or subquery WHERE expression comparison_operator [ANY | ALL] (subquery) [End of SELECT, INSERT, UPDATE, DELETE statement; or subquery]
Understanding ALL and ANY
Using the “>” comparison operator as an example, “> ALL” means greater than every value—in other words, greater than the largest value. In this way, “> ALL (1, 2, 3)” means greater than 3. “> ANY” means greater than at least ...