query_expression_body INTERSECT [ALL | DISTINCT] query_expression_body
    [INTERSECT [ALL | DISTINCT] query_expression_body]
    [...]

query_expression_body:
    See Section 15.2.14, “Set Operations with UNION, INTERSECT, and EXCEPT”

INTERSECT 将多个查询块的结果限制为所有查询块共有的那些行。示例

mysql> TABLE a;
+------+------+
| m    | n    |
+------+------+
|    1 |    2 |
|    2 |    3 |
|    3 |    4 |
+------+------+
3 rows in set (0.00 sec)

mysql> TABLE b;
+------+------+
| m    | n    |
+------+------+
|    1 |    2 |
|    1 |    3 |
|    3 |    4 |
+------+------+
3 rows in set (0.00 sec)

mysql> TABLE c;
+------+------+
| m    | n    |
+------+------+
|    1 |    3 |
|    1 |    3 |
|    3 |    4 |
+------+------+
3 rows in set (0.00 sec)

mysql> TABLE a INTERSECT TABLE b;
+------+------+
| m    | n    |
+------+------+
|    1 |    2 |
|    3 |    4 |
+------+------+
2 rows in set (0.00 sec)

mysql> TABLE a INTERSECT TABLE c;
+------+------+
| m    | n    |
+------+------+
|    3 |    4 |
+------+------+
1 row in set (0.00 sec)

与 UNION 和 EXCEPT 一样，如果未指定 DISTINCT 或 ALL，则默认值为 DISTINCT。

DISTINCT 可以从交集的两侧删除重复项，如下所示

mysql> TABLE c INTERSECT DISTINCT TABLE c;
+------+------+
| m    | n    |
+------+------+
|    1 |    3 |
|    3 |    4 |
+------+------+
2 rows in set (0.00 sec)

mysql> TABLE c INTERSECT ALL TABLE c;
+------+------+
| m    | n    |
+------+------+
|    1 |    3 |
|    1 |    3 |
|    3 |    4 |
+------+------+
3 rows in set (0.00 sec)

(TABLE c INTERSECT TABLE c 等效于上面两个语句中的第一个。)

与 UNION 一样，操作数必须具有相同数量的列。结果集列类型也与 UNION 一样确定。

INTERSECT 的优先级高于 UNION 和 EXCEPT，并且在它们之前计算，因此下面两个语句是等效的

TABLE r EXCEPT TABLE s INTERSECT TABLE t;

TABLE r EXCEPT (TABLE s INTERSECT TABLE t);

对于 INTERSECT ALL，左表中任何唯一行的最大支持重复次数为 4294967295。