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MySQL不支持INTERSECT和MINUS及其替代方法

2014-03-26 17:14:14 作者：

这篇文章主要介绍了MySQL不支持INTERSECT和MINUS情况下的替代方法,需要的朋友可以参考下

Doing INTERSECT and MINUS in MySQL

Doing an INTERSECT

An INTERSECT is simply an inner join where we compare the tuples of one table with those of the other, and select those that appear in both while weeding out duplicates. So

复制代码代码如下:

 
SELECT member_id, name FROM a 
INTERSECT 
SELECT member_id, name FROM b 

can simply be rewritten to

复制代码代码如下:

 
SELECT a.member_id, a.name 
FROM a INNER JOIN b 
USING (member_id, name) 

Performing a MINUS
To transform the statement

复制代码代码如下:

 
SELECT member_id, name FROM a 
MINUS 
SELECT member_id, name FROM b 

into something that MySQL can process, we can utilize subqueries (available from MySQL 4.1 onward). The easy-to-understand transformation is:

复制代码代码如下:

 
SELECT DISTINCT member_id, name 
FROM a 
WHERE (member_id, name) NOT IN 
(SELECT member_id, name FROM table2); 

Of course, to any long-time MySQL user, this is immediately obvious as the classical use-left-join-to-find-what-isn't-in-the-other-table:

复制代码代码如下:

 
SELECT DISTINCT a.member_id, a.name 
FROM a LEFT JOIN b USING (member_id, name) 
WHERE b.member_id IS NULL 

MySQL不支持INTERSECT和MINUS及其替代方法

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