SELECT
topics.id,
topics.forum_id,
topics.title,
SUM(posts.total) AS total_posts,
posts.max_added AS post_added
FROM topics

LEFT JOIN 
	(SELECT 
     	posts.topic_id,
     	p.total,
     	p.max_added
     	FROM posts
		
	INNER JOIN 
     		(SELECT 
                topic_id,
             	COUNT(id) AS total,
		MAX(added) AS max_added
		FROM posts 
             
                GROUP BY topic_id 

	) AS p ON p.max_added = posts.added AND p.topic_id = posts.topic_id	

) AS posts ON posts.topic_id = topics.id

GROUP BY forum_id

SELECT forum.*,
topics.id,
topics.title,
topics.topic_added,
topics.total_topics,
topics.post_added,
topics.total_posts
FROM forum

LEFT JOIN (SELECT
	id,
	forum_id,
	title,
	MAX(topics.added) AS topic_added,
	COUNT(topics.id) AS total_topics,
	posts.post_added,
	SUM(posts.total_posts) AS total_posts
	FROM topics

	LEFT JOIN (SELECT
		topic_id,
		MAX(added) AS post_added,
		COUNT(id) AS total_posts
		FROM posts
		GROUP BY topic_id
	) AS posts ON posts.topic_id = topics.id

	GROUP BY topics.forum_id

) AS topics ON topics.forum_id = forum.id

GROUP BY forum.id

SELECT 
forum.*,
maxi.last_added,
maxi.total_posts,
maxi.total_topics,
topics.id AS topic_id,
topics.title AS topic_title,
topics.added,
users.id AS userid,
users.username,
users.class
FROM forum
LEFT JOIN (
	SELECT 
	t.forum_id,
	MAX(COALESCE(p.added, t.added)) AS last_added,
	COUNT(p.id) AS total_posts,
	COUNT(DISTINCT(t.id)) AS total_topics
	FROM topics t
	LEFT JOIN posts p ON p.topic_id = t.id
	GROUP BY t.forum_id
) maxi ON maxi.forum_id = forum.id
LEFT JOIN posts p ON maxi.last_added = p.added
LEFT JOIN topics t ON maxi.last_added = t.added
LEFT JOIN topics ON topics.id = COALESCE(p.topic_id, t.id)
LEFT JOIN users ON users.id = COALESCE(p.owner, t.owner)
GROUP BY forum.id
ORDER BY forum.srt ASC