继续浏览精彩内容
慕课网APP
程序员的梦工厂
打开
继续
感谢您的支持,我会继续努力的
赞赏金额会直接到老师账户
将二维码发送给自己后长按识别
微信支付
支付宝支付

MySQL不支持INTERSECT和MINUS及其替代方法

喵喵一只汪
关注TA
已关注
手记 315
粉丝 86
获赞 467

           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
                       

打开App,阅读手记
0人推荐
发表评论
随时随地看视频慕课网APP