Re: I don't understand something...

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...

--
Best regards,
Alexander Pyhalov,
system administrator of Computer Center of Southern Federal University