Actually, I just noticed the real problem.
Try this instead,
SELECT Item.Item;
FROM Item ;
WHERE item.item NOT IN;
(SELECT Itemparent from BOM);
GROUP BY Item.Item;
>Christian,
>
>Try isnull() instead of value=null
>
>SELECT Item.Item
>FROM Item LEFT JOIN BOM ON Item.Item = BOM.ItemParent
>WHERE isnull(BOM.ItemParent);
>GROUP BY Item.Item;