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

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   +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

EXCEPT– 返回第一个表中有、第二个表中没有的数据

SQL Server 支持

MySQL 不支持

实现相同功能的 SQL 如下：