SQL EXCEPT 语句

SQL EXCEPT语句/运算符用于连接两个 SELECT 语句结果集。返回在第一个 SELECT 语句的结果集中存在但是在第二个 SELECT 语句结果集中不存在的行。这也就是说 EXCEPT 仅返回在第二个 SELECT 语句中不存在的行。

使用 EXCEPT 运算符时的规则和UNION运算符的规则相同。MySQL 不支持 EXCEPT 运算符。

语法

EXCEPT的基本语法如下。

SELECT column1 [, column2 ]
FROM table1 [, table2 ]
[WHERE condition]

EXCEPT

SELECT column1 [, column2 ]
FROM table1 [, table2 ]
[WHERE condition]

示例

现在我们看如下的两张表

1. 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 |
+----+----------+-----+-----------+----------+

2. ORDERS 表

+-----+---------------------+-------------+--------+
|OID  | DATE                | CUSTOMER_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，让我们在 SELECT 语句中连接这两个表，如下所示。

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;

结果如下。

+----+---------+--------+---------------------+
| ID | NAME    | AMOUNT | DATE                |
+----+---------+--------+---------------------+
|  1 | Ramesh  |   NULL | NULL                |
|  5 | Hardik  |   NULL | NULL                |
|  6 | Komal   |   NULL | NULL                |
|  7 | Muffy   |   NULL | NULL                |
+----+---------+--------+---------------------+