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我有一个 mysql 查询我在对发件人的最新消息进行排序时遇到问题这是我的以下查询：

   SELECT 
        `Mes`.`fromid`, 
        `Mes`.`is_read`, 
        `Mes`.`id` AS `mesid`, 
        `Mes`.`message`,
        max(Mes.date) AS `date`, 
        `User`.`username`, 
        `User`.`MemberID` AS `Uid` 
   FROM `messages` AS `Mes` 
   INNER JOIN `users` AS `User` ON User.MemberID = Mes.fromid 
   WHERE (Mes.toid = 5 AND Mes.fromid <> 5) 
   GROUP BY `Mes`.`fromid` 
   ORDER BY `date` DESC

这是我数据库中的表：用户表

MemberID      UserName     Email             Password
1             User1       user1@gmail.com   123456
2             User2       user2@gmail.com   123456
3             User3       user3@gmail.com   123456
4             User4       user4@gmail.com   123456
5             User5       user5@gmail.com   123456

消息表：

id      fromid     toid    message         is_read    date  
1       5          2       hello test 1    1          2012-08-24 01:00:00
2       2          5       hello test 2    1          2012-08-24 02:00:00
3       3          5       hello test 3    1          2012-08-24 03:00:00
4       4          5       hello test 4    1          2012-08-24 04:00:00
5       2          5       hello test 5    1          2012-08-25 05:00:00

和我的查询的输出：

SELECT 
     `Mes`.`fromid`, 
     `Mes`.`is_read`, 
     `Mes`.`id` AS `mesid`,
     `Mes`.`message`, 
     max(Mes.date) AS `date`, 
     `User`.`username`, 
     `User`.`MemberID` AS `Uid` 
FROM `messages` AS `Mes` 
INNER JOIN `users` AS `User` ON User.MemberID = Mes.fromid 
WHERE (Mes.toid = 5 AND Mes.fromid <> 5) 
GROUP BY `Mes`.`fromid` 
ORDER BY `date` DESC

是 ：

USERNAME     MESSAGE          DATE
user2        hello test 2     2012-08-25 05:00:00
user4        hello test 4     2012-08-25 04:00:00
user4        hello test 3     2012-08-25 03:00:00

如果您注意到从日期排序是正确的，但最新消息是不正确的。我想要这样的输出。

USERNAME     MESSAGE          DATE
user2        hello test 5     2012-08-25 05:00:00
user4        hello test 4     2012-08-25 04:00:00
user4        hello test 3     2012-08-25 03:00:00

而不是消息“ hello test 2 ”，我想对最新消息“ hello test 5 ”进行排序

任何人都可以帮助我的问题？

太感谢了...

4

1 回答 1

1

应该是这样的

SELECT  *                              // -- select the columns you want
FROM    Messages a
            INNER JOIN
            (
                SELECT  fromid, toid, MAX(`date`) maxDATE
                FROM    Messages
                GROUP BY fromid, toid
            ) b ON a.fromID = b.fromID AND
                   a.toid = b.toid AND
                   a.`date` = b.maxDATE
            INNER JOIN users c
                ON c.MemberID = a.fromID
WHERE   a.toid = 5 AND a.fromid <> 5
ORDER BY `date` DESC
于 2012-09-06T00:52:21.410 回答