except-clause.html

EXCEPT 子句

EXCEPT 子句/运算符用于将两个 SELECT 语句结合在一起，并返回第一个 SELECT 语句的结果中那些不存在于第二个 SELECT 语句结果的记录。这就意味着，EXCEPT 仅返回那些不存在于第二个 SELECT 语句结果的记录（差集）。

EXCEPT 运算符遵循同 UNION 运算符一样的规则。MySQL 不支持 EXCEPT 运算符。

EXCEPT子句的基本语法如下所示：

SELECT column1 [, column2 ]

FROM table1 [, table2 ]

[WHERE condition]

EXCEPT

SELECT column1 [, column2 ]

FROM table1 [, table2 ]

[WHERE condition]

这里给定的条件可以是任何根据你自己的需要而得出的表达式。

示例：

考虑如下两个表格，（a）CUSTOMERS 表：

+----+----------+-----+-----------+----------+

| ID | NAME     | AGE | ADDRESS   | SALARY   |

+----+----------+-----+-----------+----------+

|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |

|  2 | Khilan   |  25 | Delhi     |  1500.00 |

|  3 | kaushik  |  23 | Kota      |  2000.00 |

|  4 | Chaitali |  25 | Mumbai    |  6500.00 |

|  5 | Hardik   |  27 | Bhopal    |  8500.00 |

|  6 | Komal    |  22 | MP        |  4500.00 |

|  7 | Muffy    |  24 | Indore    | 10000.00 |

+----+----------+-----+-----------+----------+

（b）ORDERS 表：

+-----+---------------------+-------------+--------+

| OID | DATE                |          ID | AMOUNT |

+-----+---------------------+-------------+--------+

| 102 | 2009-10-08 00:00:00 |           3 |   3000 |

| 100 | 2009-10-08 00:00:00 |           3 |   1500 |

| 101 | 2009-11-20 00:00:00 |           2 |   1560 |

| 103 | 2008-05-20 00:00:00 |           4 |   2060 |

+-----+---------------------+-------------+--------+

现在，让我将这两个表的 EXCEPT 查询的结果结合在一起：

SQL> SELECT  ID, NAME, AMOUNT, DATE

     FROM CUSTOMERS

     LEFT JOIN ORDERS

     ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID

EXCEPT

     SELECT  ID, NAME, AMOUNT, DATE

     FROM CUSTOMERS

     RIGHT JOIN ORDERS

     ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID;

其结果如下所示：

+----+---------+--------+---------------------+

| ID | NAME    | AMOUNT | DATE                |

+----+---------+--------+---------------------+

|  1 | Ramesh  |   NULL | NULL                |

|  5 | Hardik  |   NULL | NULL                |

|  6 | Komal   |   NULL | NULL                |

|  7 | Muffy   |   NULL | NULL                |

+----+---------+--------+---------------------+

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++   分割线   +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

-- 测试表，与测试数据

CREATE TABLE union_tab_1 (

id INT,

val VARCHAR(10)

);

CREATE TABLE union_tab_2 (

id INT,

val VARCHAR(10)

);

INSERT INTO union_tab_1 VALUES(1, 'A');

INSERT INTO union_tab_1 VALUES(2, 'B');

INSERT INTO union_tab_1 VALUES(3, 'C');

INSERT INTO union_tab_2 VALUES(1, 'A');

INSERT INTO union_tab_2 VALUES(2, 'B');

INSERT INTO union_tab_2 VALUES(4, 'D');

EXCEPT– 返回第一个表中有、第二个表中没有的数据

SQL Server 支持

1> SELECT * FROM union_tab_1

2> EXCEPT

3> SELECT * FROM union_tab_2;

4> go

id val

----------- ----------

3 C

(1 行受影响)

1> SELECT * FROM union_tab_2

2> EXCEPT

3> SELECT * FROM union_tab_1;

4> go

id val

----------- ----------

4 D

(1 行受影响)

MySQL 不支持

实现相同功能的 SQL 如下：

SELECT

DISTINCT union_tab_1.*

FROM

union_tab_1 LEFT JOIN union_tab_2

ON (union_tab_1.id = union_tab_2.id

AND union_tab_1.val = union_tab_2.val)

WHERE

union_tab_2.id IS NULL;

+------+------+

| id | val |

+------+------+

| 3 | C |

+------+------+

1 row in set (0.00 sec)

except

SQL中EXCEPT函数在 Mysql 和 sqlServer 中的替代方法

示例摘自：极客代码：http://wiki.jikexueyuan.com/project/sql/useful-functions/except-clause.html

EXCEPT 子句

示例：