用mysql INNER JOIN命令

Question

我从内部联接的两个表中获取记录，但是我没有得到正确的结果。

这是我的代码：

   real_query = "SELECT DISTINCT user.id AS uid, user.name AS unm, user.profile_pic AS upic, user_message.message_by_id AS message_by_id
                 FROM user INNER JOIN
                      user_message
                      ON user.id = user_message.message_by_id 
                 where (user_message.message_to_id = '".$sess."' AND 
                        user_message.receiver_deleted = 'No')
                 group by user_message.id, user_message.sent_on
                 order by user_message.id DESC ";

问题是，我想回复用户表中的那些用户名，按user_message.id排序，但我没有得到我想要的结果。