Is IN with the multiple of the same values slower?

问题

For example, is this noticeably slower:

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

Than this:

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

SQL Server 2008 R2.

Thanks!

回答1:

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

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.

来源：https://stackoverflow.com/questions/10901238/is-in-with-the-multiple-of-the-same-values-slower