Mysql的GROUP BY和獨特的價值

我有一個表在MySQL：Mysql的GROUP BY和獨特的價值

 
SID DID MessageType DateOf Message 
1 255 LOG  2010-01-17 15:02:05 Log msg 1  
2 255 USER 2010-01-17 19:02:05 User msg 1 
3 211 LOG  2010-01-17 15:06:55 Log msg 2  
4 211 ADMIN 2010-01-17 22:06:55 Admin msg 1

我需要得到最後（通過DateOf）消息和消息類型，細分電子郵件由DID，下令DateOf DESC

權結果將是：

 
DID MessageType DateOf Message 
211 ADMIN  2010-01-17 22:06:55 Admin msg 1 
255 USER  2010-01-17 19:02:05 User msg 1

我該如何做這個select查詢？ MySQL 5.1

來源

2010-01-17 x17az

SELECT * FROM `test` WHERE (DID,DateOf) IN (
    SELECT DID,MAX(DateOf) FROM `test` GROUP BY DID 
) GROUP BY DID ORDER BY DateOf DESC

子查詢爲每個DID選擇max DateOf。外部查詢選擇具有這些DateOf和DID的行。 GROUP BY在外部查詢中確保每個DID的結果中只有一行（如果表中有多個具有相同DID和DateOf的行，則它將返回其中一個，而沒有任何特定順序）。

來源

2010-01-17 13:59:07

SELECT * FROM test t JOIN (
    SELECT DID, MAX(DateOf) AS DateOf FROM test GROUP BY DID 
) t2 ON (t.DID = t2.DID AND t.DateOf = t2.DateOf) 
ORDER BY t.DateOf DESC;

另一種解決方案：

SELECT * FROM test t WHERE DateOf = (
    SELECT MAX(DateOf) FROM test t2 WHERE t2.DID = t.DID 
) ORDER BY DateOf DESC;

當我解決這個前一段時間我用Google搜索這個有用的文章：http://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/

來源

2010-01-17 14:20:41 Messa

Mysql的GROUP BY和獨特的價值

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