在MySQL中使用LIMIT 1 [英] Using LIMIT 1 in MySQL

问题描述

在MySQL中，在查询末尾添加LIMIT 1的适当时间是合适的.我通常在DELETE中添加它，但是我已经看到它与INSERT a甚至UPDATE一起使用.是矫kill过正还是好的做法?

When is it appropriate to add LIMIT 1 at the end of the query in MySQL. I normally add it in DELETE but I've seen it being used with INSERT a and even UPDATE. Is it an overkill or a good practice?

推荐答案

好吧，如果您使用EXPLAIN，您会发现它加快了速度，一旦发现一个结果，它就会停止.

Well, if you use EXPLAIN you'll see that it speeds things up, as once it's found one result, it stops.

这也是一种故障保护–如果您知道更新的插入只会影响一行，通过指定它，可以保证它不会出错并弄乱多行.

It's also a failsafe – if you know your insert of update should only ever affect one row, by specifying it, you are guaranteeing that it won't ever go wrong and mess up multiple rows.

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