13.2.10.3 Subqueries with ANY, IN, or SOME

Syntax:

Where comparison_operator is one of these operators:

= > < >= <= <> !=

The ANY keyword, which must follow a comparison operator, means "return TURE if the comparison is TRUE for ANY of the values in the column that subquery returns." For example:

SELECT s1 FROM t1 WHERE s1 > ANY(SELECT s1 FROM t2);

Suppose that there is a row in table t1 containing (10). The expression is TRUE if table t2 contains (21, 14, 7) because there is a value 7 in t2 that is less than 10. The expression is FALSE if table t2 contains(20, 10), or if table t2 is empty. The expression is unknown(that is, NULL) if table t2 contains (NULL, NULL, NULL).

When used with a subquery, the word IN is an alias for = ANY. Thus, these two statements are the same:

SELECT s1 FROM t1 WHERE s1 <> ANY (SELECT s1 FROM t2);
SELECT s1 FROM t1 WEHRE s2 <> SOME (SELECT s1 FROM t2);

Use of the word SOME is rare, but this example shows why it might be useful. To most people, the English phrase 'a is not equal to any b' means "there is no b which is equal to a", but that is not what is meant by the SQL syntax. The syntax means "there is some b to which a is not equal." Using <> SOME instead helps ensure that everyone understands the true meaning of the query.