EXPLAIN EXTENDED
SELECT c.*,
       IFNULL(u.nickname, 0) as nickname,
       IFNULL(u.login, 0) as login,
       IFNULL(u.is_deleted, 0) as is_deleted,
       IFNULL(p.imageurl, 0) as imageurl,
       IFNULL(p.gender, 0) as gender
FROM cms_comments c
LEFT JOIN cms_users u ON u.id = c.user_id
LEFT JOIN cms_user_profiles p ON p.user_id = u.id
WHERE c.published = 1
  AND (c.target IN ('mapnews','mapitem','blog','article','palbum','photo','userphoto'))
  AND (c.is_hidden=0)
ORDER BY c.pubdate DESC
LIMIT 0, 6