mysql - 我想使用 group by 在 mysql 中获取最后一行

Question

SELECT * FROM msg_messages m 
JOIN msg_status s on m.messageId = s.messageId 
JOIN msg_threads t ON t.threadId = m.threadId 
JOIN users u ON u.userId = s.userId 
WHERE t.threadId = 1 
GROUP BY u.userId ORDER BY `m`.`date` DESC 

这是给我每条记录的第一个索引的查询。但我想获得每个组的最新索引.. 我尝试了很多方法，但结果一无所获。用户：

Answer 1

这个怎么样：

SELECT * FROM msg_messages m 
JOIN msg_status s on m.messageId = s.messageId 
JOIN msg_threads t ON t.threadId = m.threadId 
JOIN users u ON u.userId = s.userId 
GROUP BY u.userId 
having max (`m`.`date`)
ORDER BY `m`.`date` DESC 

我修改了我的查询

having max (`t`.`threadId`)

至

having max (`m`.`date`)

Answer 2

您可以在 DESC 之后使用 LIMIT 1 ，然后您将获得最后一条记录。示例： DESC 限制 1；

Answer 3

试试这个代码

SELECT * FROM msg_messages m 
JOIN msg_status s on m.messageId = s.messageId 
JOIN msg_threads t ON t.threadId = m.threadId 
JOIN users u ON u.userId = s.userId 
WHERE t.threadId = 1 
GROUP BY u.userId ORDER BY `m`.`date` DESC LIMIT 0,1