如果不存在则插入 [英] INSERT if not Exist Mysql

问题描述

我有这张桌子

id     follow_id    follower_id
 1  |       2     |      3
 2  |       2     |      4
 3  |       2     |      5
 4  |       2     |      6
 5  |       3     |      7
 6  |       3     |      8

我想跳过如果我尝试插入"couple" follow_id 2，follower_id 3，而无需对性能进行子查询

I'd like to skip If i try to insert the "couple" follow_id 2, follower_id 3 without do subquery for the performance

我可以在重复键更新中执行INSERT ...操作吗?

can I do INSERT... ON DUPLICATE KEY UPDATE or something of this?

更新，适用于symfony用户

回答后.我使用Symfony，并且这样做

after answers. i Use Symfony, and for do

UNIQUE INDEX followee_and_follower (follow_id,follower);

http://docs.doctrine- project.org/en/2.0.x/reference/annotations-reference.html#uniqueconstraint

推荐答案

其官方语法是

INSERT IGNORE ...

但是，在您的情况下，这样做实际上更可取

However, in your case it may actually be preferable to do

INSERT ... ON DUPLICATE KEY UPDATE id=id

请参见

See benchmarks. In my experience, this hack only improves performance if you've got a primary key--the optimizer won't recognize the no-op if you do follower_id = follower_id.

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