1345RE: 1344MYSQL IN clause is expensive?

Thursday, December 10, 2009

yes it is, it is better to do a left join on the table and exclude in the where clause where one of the fields is not null

> Date: Wed, 9 Dec 2009 23:20:19 -0800
> Subject: 1344MYSQL IN clause is expensive?
> From: natarajanonline@gmail.com
> To: it_help_desk@googlegroups.com
> Hi,
> I would like to use SELECT * from users where userid IN(SELECT userid
> from user_book where availability=1)
> In the above subquery, it can return 1000 of records. Whether this
> operation is expensive?
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