MySQL In Clause 在列表具有重复元素且未排序的情况下的性能 [英] MySQL In Clause performace in case of list have duplicate elements and not sorted

问题描述

如果 mysql 中 IN 子句的值列表有重复值且未排序是否会影响查询性能.

if list of value for IN clause in mysql have duplicate values and not sorted does it affect performance of query.

例如

SELECT * FROM `t1` WHERE `id` IN (2,2,3,1,1);

v/s

SELECT * FROM `t1` WHERE `id` IN (1,2,3);

推荐答案

MySQL 将在优化阶段去除不同的值并对其进行排序.

MySQL will get rid of distinct values and sort them on optimizing stage.

这会对性能产生轻微影响，但对于大多数实际查询，您不会注意到任何差异(以毫秒为单位).

This will marginally affect performance, but with most real-world queries you won't notice any difference (it's order of milliseconds).

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