您需要创建一个子查询，该子查询通过sender_id返回给定接收者的最大消息ID，并将其加入message表以获取所有其他字段：
SELECt m.* FROM `message` AS mINNER JOIN (SELECt sender_id, MAX(message_date) as md FROM message WHERe `receiver_id` =1 GROUP BY sender_id) AS tON m.message_date=t.md and m.sender_id=t.sender_idWHERe `receiver_id` =1
