forum join

select count(t.*) as aantal_topics, count(r.*) 
from categories as c 
inner join  topics as t on (c.id = t.cat_id) 
inner join reacties as r on (t.id = r.topic_id) 
where c.id=... 
group by t.id

SELECT count(t.*) AS aantal_topics, count(r.*) 
FROM categories AS c 
INNER JOIN  topics AS t ON (c.id = t.cat_id) 
INNER JOIN reacties AS r ON (t.id = r.topic_id) 
WHERE c.id=... 
GROUP BY t.id

dit is de code nu:
SELECT forum.*, forum_categorie.*, fo_on.fo_on_id, IFNULL(fo_on.topics,0) AS topics, IFNULL(fo_re.reacties, 0) AS reacties
FROM forum 
JOIN forum_categorie ON(forum.forum_id=forum_categorie.fo_ca_sub)
LEFT JOIN (SELECT fo_on_id, fo_on_sub
           ,      COUNT(1) AS topics
           FROM   forum_onderwerp
           GROUP BY
                  fo_on_sub) fo_on  
       ON (forum_categorie.fo_ca_id = fo_on.fo_on_sub) 
LEFT JOIN(SELECT fo_re_sub, count(1) AS reacties 
			FROM forum_reacties
			GROUP BY fo_re_sub) fo_re
		ON (fo_on.fo_on_id=fo_re.fo_re_sub)
ORDER BY forum_categorie.fo_ca_sub, forum_categorie.fo_ca_id ASC

dit is de code nu:
SELECT forum.*, forum_categorie.*, fo_on.fo_on_id, IFNULL(fo_on.topics,0) AS topics, IFNULL(fo_re.reacties, 0) AS reacties
FROM forum 
JOIN forum_categorie ON(forum.forum_id=forum_categorie.fo_ca_sub)
LEFT JOIN (SELECT fo_on_id, fo_on_sub
           ,      COUNT(1) AS topics
           FROM   forum_onderwerp
           GROUP BY
                  fo_on_sub) fo_on  
       ON (forum_categorie.fo_ca_id = fo_on.fo_on_sub) 
LEFT JOIN(SELECT fo_re_sub, count(1) AS reacties 
			FROM forum_reacties
			GROUP BY fo_re_sub) fo_re
		ON (fo_on.fo_on_id=fo_re.fo_re_sub)
ORDER BY forum_categorie.fo_ca_sub, forum_categorie.fo_ca_id ASC