DELETE Difference NOT IN vs NOT EXISTS

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mysql

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DELETE Difference NOT IN vs NOT EXISTS

+1 A:

These two queries should, to my knowledge, achieve the same results (since the query checks for the same data - only the second one does it in a more elegant manner maybe).

Pawel J. Wal 2010-02-06 10:00:16

Thanks Bro..... :D

Shahmir Javaid 2010-02-06 10:03:07

Any body can Confirm 100%... sry Pawel need to be sure, maybe is not good when this thing is released. xD

Shahmir Javaid 2010-02-06 10:08:05

+3 A:

I haven't tested it, but they are most likely not equivalent. The NOT EXISTS form would make sense if used with a correlated subquery. But your subquery doesn't contain any reference to the outer query, so probably the second form won't delete any rows at all.

Also, presence of NULLs in the table may make these two forms act very differently.

Marek Rocki 2010-02-06 11:09:49

Thanks. Is there a way around it. Could i use another query that will solve my NOT IN problem?

Shahmir Javaid 2010-02-07 05:58:23

Could you post an example of the correlated query. It would be appreciated :D

Shahmir Javaid 2010-02-07 07:43:32

ansaurus

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DELETE Difference NOT IN vs NOT EXISTS

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