postgresql7.1 select substring(tree_sortkey, 0, 9) as father_tree_sortkey from forums_messages where message_id=$message(message_id) select parent_id from forums_messages where forum_id = $message(forum_id) and tree_sortkey between tree_left('$father_tree_sortkey') and tree_right('$father_tree_sortkey') order by tree_sortkey desc