Subqueries | 1 | +--------+ mysql>  (SELECT 1 AS result UNION SELECT 3 UNION SELECT 2) ORDER BY result LIMIT 1 OFFSET 1 INTO @var; mysql>  SELECT @var; +------+ | @var | +------+ | 2 | +------+ Parenthesized query expressions are also used as query expressions, so a query expression, usually composed of query blocks, may also consist of parenthesized query expressions: (SELECT * FROM t1 ORDER BY a) UNION (SELECT * FROM t2 ORDER BY b) ORDER BY z; Query blocks may have trailing  ORDER BY  and  LIMIT  clauses, which are applied before the outer  UNION and  ORDER BY  and  LIMIT . You cannot have a query block with a trailing  ORDER BY  or  LIMIT , without wrapping it in parentheses, but parentheses may be used for enforcement in various ways: (SELECT 1 LIMIT 1) UNION (SELECT 2 LIMIT 1); (SELECT 1 LIMIT 1) UNION (SELECT 2 LIMIT 1) LIMIT 1; SELECT 1 UNION SELECT 2 LIMIT 1; (SELECT 1 LIMIT 1) UNION SELECT 2 LIMIT 1; The syntax described in this section is subject to certain restrictions: A subquery is a  SELECT  statement within another statement. All subquery forms and operations that the SQL standard requires are supported, as well as a few features that are MySQL-specific. 2682 •To enforce  LIMIT  on each query block: •To enforce  LIMIT  on both query blocks and the entire query expression: •To enforce  LIMIT  on the entire query expression (with no parentheses): •Hybrid enforcement:  LIMIT  on the first query block and on the entire query expression: •If  ORDER BY  occurs within a parenthesized query expression and also is applied in the outer query, the results are undefined and may change in a future version of MySQL. The same is true if  LIMIT  occurs within a parenthesized query expression and also is applied in the outer query. •A trailing  INTO  clause for a query expression is not permitted if there is another  INTO  clause inside parentheses. •Parenthesized query expressions do not permit multiple levels of  ORDER BY  or  LIMIT  operations. For example: mysql>  (SELECT ’a’ UNION SELECT ’b’ LIMIT 1) LIMIT 2; ERROR 1235 (42000): This version of MySQL doesn’t yet support ’parenthesized query expression with more than one external level of ORDER/LIMIT operations’ 13.2.11 Subqueries