postgresql7.3 SELECT b.subject AS subject, b.message_id AS thread_id, a.message_id AS message_id FROM (SELECT message_id, tree_sortkey, posting_date FROM forums_messages WHERE forum_id IN (SELECT forum_id FROM forums_forums WHERE package_id = :package_id and enabled_p = 't') ORDER BY posting_date DESC LIMIT $n) a, forums_messages b WHERE b.parent_id IS NULL AND b.tree_sortkey = tree_root_key(a.tree_sortkey) AND b.forum_id IN (SELECT forum_id FROM forums_forums WHERE package_id = :package_id and enabled_p = 't'); SELECT subject, message_id FROM forums_messages_approved WHERE forum_id IN (SELECT forum_id FROM forums_forums WHERE package_id = :package_id and enabled_p = 't') AND parent_id IS NULL ORDER BY posting_date DESC LIMIT $n