SELECT

[Ilja]

yo,

kann auch nur raten, was du meinst aber versuch mal folgende query...

SELECT f.id, f.thema, f.forum_id, f.date, t.id, t.beitrag, t.user, t.zeit, t.sub_forum_id
FROM Sub_Forum AS f
LEFT JOIN Sub_Thema AS t ON (t.sub_forum_id = f.id)
WHERE f.forum_id=$kategorie

Ilja