Re: I don't understand something... - Mailing list pgsql-general

On Mon, Oct 03, 2011 at 11:48:45AM +0400, Alexander Pyhalov wrote:
> On 10/03/2011 11:19, Achilleas Mantzios wrote:
> >Alexander, that's a classic one,
> >rewrite your last query as :
> >
> >SELECT count(employee_id) from employees where employee_id not in
> >    (select manager_id from employees WHERE manager_id  IS NOT NULL);
> >
> >NULLS semantics are sometimes not so obvious.
>
> Thanks.
> It's confusing, that IN check works as expected, but NOT IN works
> this way...

If I might plug:
http://www.depesz.com/index.php/2008/08/13/nulls-vs-not-in/

Best regards,

depesz

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