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 8.0.22 及更高版本支持根据上述语法的带括号的查询表达式。SELECT在最简单的情况下，带括号的查询表达式包含返回结果集 的单个 或其他语句，并且没有以下可选子句：

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

TABLE t;

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

（从 MySQL 8.0.19 开始 支持TABLEand 语句。）VALUES

带括号的查询表达式还可以包含由一个或多个集合操作链接的查询，例如 UNION, 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 |
+------+

除了UNION， INTERSECT和EXCEPTset 运算符从 MySQL 8.0.31 开始可用。 在和INTERSECT之前 执行，因此以下两个语句是等价的： UNIONEXCEPT

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能由括号查询表达式组成：

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

查询块可能有尾随ORDER BY和 LIMIT子句，它们在外部集合操作、ORDER BY和 之前应用LIMIT。

您不能有一个带有尾随ORDER BY或LIMIT不包含在括号中的查询块，但括号可以以多种方式用于强制执行：

本节中描述的语法受到某些限制：