select * from (
SELECT
    if(com.comment_approved = '1' and com.user_id > 0, com_u.display_name, u.display_name) as display_name,
    com.comment_author,
    if(p.post_type = 'reply', t.post_title, p.post_title) as title,
    if(com.comment_approved = '1', com.comment_ID, p.ID) as post_id,
    if(com.comment_approved = '1', com.user_id, p.post_author) as author_id,
    if(com.comment_approved = '1', unix_timestamp(com.comment_date), unix_timestamp(p.post_date)) as post_date,
    if(com.comment_approved = '1', SUBSTRING(com.comment_content, 1, 200), SUBSTRING(p.post_content, 1, 200)) as content,
    if(com.comment_approved = '1', 'comment', p.post_type) as type,
    if(p.post_type = 'reply', ifnull(p.post_parent,0), p.ID) as post_parent,
        max(post_date) as max_post_date
FROM `wp_posts` as p
LEFT JOIN `wp_users` as u on u.ID = p.post_author
LEFT JOIN `wp_posts` as t on t.ID = p.post_parent
LEFT JOIN `wp_comments` as com on com.comment_post_ID = p.ID
LEFT JOIN `wp_users` as com_u on com_u.ID = com.user_id
WHERE ((p.post_type = 'reply' OR p.post_type = 'topic' OR p.post_type = 'post')
    AND p.post_status = 'publish'
    AND p.post_content <> '')
    OR com.comment_approved = '1'
GROUP BY post_parent)
ORDER BY max_post_date DESC
LIMIT 0,12