On Tue, 05 Feb 2008 11:11:21 +0100, Sebastian <haja.sebastian@gmail.com>
wrote:

> Hi
>
> I have 2 tables:
>
> [general_libcounty]:
> - id_libCounty (PK)
> - libCounty_name
> - id_libCountry
>
> [general_libtown]:
> - id_libTown (PK)
> - libTown_name
> - id_libCounty (FK)
>
> How to select all counties what don't have any towns in
> general_libtown table
>
> Relation:
> general_libcounty.id_libCounty=general_libtown.id_ libCounty

Assuming there's nu NULL allowed in general_libtown.id_libCounty:

SELECT c.id_libCounty
FROM general_libcounty c
LEFT JOIN general_libtown t
ON c.id_libCounty = t.id_libCounty
WHERE t.id_libCounty IS NULL

If there are NULLs in general_libtown.id_libCounty:

SELECT c.id_libCounty, COUNT(t.id_libTown) as countTowns
FROM general_libcounty c
LEFT JOIN general_libtown t
ON c.id_libCounty = t.id_libCounty
GROUP BY c.id_libCounty
HAVING countTowns = 0
--
Rik Wasmus