parenthesized_query_expression:
    ( query_expression [order_by_clause] [limit_clause] )
      [order_by_clause]
      [limit_clause]
      [into_clause]

query_expression:
    query_block [set_op query_block [set_op query_block ...]]
      [order_by_clause]
      [limit_clause]
      [into_clause]

query_block:
    SELECT ... | TABLE | VALUES

order_by_clause:
    ORDER BY as for SELECT

limit_clause:
    LIMIT as for SELECT

into_clause:
    INTO as for SELECT

set_op:
    UNION | INTERSECT | EXCEPT

MySQL 8.4 根据前面的语法支持括号查询表达式。最简单地说，括号查询表达式包含单个 SELECT 或其他返回结果集的语句，并且没有后续的可选子句。

(SELECT 1);
(SELECT * FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'mysql');

TABLE t;

VALUES ROW(2, 3, 4), ROW(1, -2, 3);

括号查询表达式还可以包含由一个或多个集合操作（例如 UNION）链接的查询，并以任何或所有可选子句结尾。

mysql> (SELECT 1 AS result UNION SELECT 2);
+--------+
| result |
+--------+
|      1 |
|      2 |
+--------+
mysql> (SELECT 1 AS result UNION SELECT 2) LIMIT 1;
+--------+
| result |
+--------+
|      1 |
+--------+
mysql> (SELECT 1 AS result UNION SELECT 2) LIMIT 1 OFFSET 1;
+--------+
| result |
+--------+
|      2 |
+--------+
mysql> (SELECT 1 AS result UNION SELECT 2)
       ORDER BY result DESC LIMIT 1;
+--------+
| result |
+--------+
|      2 |
+--------+
mysql> (SELECT 1 AS result UNION SELECT 2)
       ORDER BY result DESC LIMIT 1 OFFSET 1;
+--------+
| result |
+--------+
|      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 |
+------+

INTERSECT 在 UNION 和 EXCEPT 之前起作用，因此以下两条语句是等效的。

SELECT a FROM t1 EXCEPT SELECT b FROM t2 INTERSECT SELECT c FROM t3;

SELECT a FROM t1 EXCEPT (SELECT b FROM t2 INTERSECT SELECT c FROM t3);

括号查询表达式也用作查询表达式，因此通常由查询块组成的查询表达式也可以由括号查询表达式组成。

(TABLE t1 ORDER BY a) UNION (TABLE t2 ORDER BY b) ORDER BY z;

查询块可能具有尾随的 ORDER BY 和 LIMIT 子句，这些子句在外部集合操作、ORDER BY 和 LIMIT 之前应用。

不能在没有用括号括起来的查询块中使用尾随的 ORDER BY 或 LIMIT，但括号可以以多种方式用于强制执行。

本节描述的语法受某些限制