具有相同值倍数的 IN 是否更慢? [英] Is IN with the multiple of the same values slower?

问题描述

例如，这是否明显变慢了:

For example, is this noticeably slower:

DELETE FROM [table] WHERE [REOID] IN ( 1, 1, 1, 2, 2, 1, 3, 5)

比这个:

DELETE FROM [table] WHERE [REOID] IN ( 1, 2, 3, 4)

SQL Server 2008 R2.

SQL Server 2008 R2.

谢谢！

推荐答案

大多数引擎会在解析阶段消除常量 IN 列表中的重复项.

Most engines would eliminate duplicates in the constant IN list on parsing stage.

这样的查询会比使用非重复列表的查询稍微慢一点，会产生相同的计划，并且在大多数实际场景中，您几乎不会注意到任何区别.

Such a query would parse marginally slower than that with a non-duplicated list, will produce the same plan and with most real-world scenarios, you will hardly notice any difference.

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