15.2.15.4 Subqueries with ALL

Syntax:

operand comparison_operator ALL (subquery)

The word ALL, which must follow a comparison operator, means “return TRUE if the comparison is TRUE for ALL of the values in the column that the subquery returns.” For example:

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

Suppose that there is a row in table t1 containing (10). The expression is TRUE if table t2 contains (-5,0,+5) because 10 is greater than all three values in t2. The expression is FALSE if table t2 contains (12,6,NULL,-100) because there is a single value 12 in table t2 that is greater than 10. The expression is unknown (that is, NULL) if table t2 contains (0,NULL,1).

Finally, the expression is TRUE if table t2 is empty. So, the following expression is TRUE when table t2 is empty:

SELECT * FROM t1 WHERE 1 > ALL (SELECT s1 FROM t2);

But this expression is NULL when table t2 is empty:

SELECT * FROM t1 WHERE 1 > (SELECT s1 FROM t2);

In addition, the following expression is NULL when table t2 is empty:

SELECT * FROM t1 WHERE 1 > ALL (SELECT MAX(s1) FROM t2);

In general, tables containing NULL values and empty tables are “edge cases.” When writing subqueries, always consider whether you have taken those two possibilities into account.

NOT IN is an alias for <> ALL. Thus, these two statements are the same:

SELECT s1 FROM t1 WHERE s1 <> ALL (SELECT s1 FROM t2);
SELECT s1 FROM t1 WHERE s1 NOT IN (SELECT s1 FROM t2);

MySQL 8.0.19 supports the TABLE statement. As with IN, ANY, and SOME, you can use TABLE with ALL and NOT IN provided that the following two conditions are met:

• The table in the subquery contains only one column

• The subquery does not depend on a column expression

For example, assuming that table t2 consists of a single column, the last two statements shown previously can be written using TABLE t2 like this:

SELECT s1 FROM t1 WHERE s1 <> ALL (TABLE t2);
SELECT s1 FROM t1 WHERE s1 NOT IN (TABLE t2);

A query such as SELECT * FROM t1 WHERE 1 > ALL (SELECT MAX(s1) FROM t2); cannot be written using TABLE t2 because the subquery depends on a column expression.