MySQL的 - 組由具有多個列

Question

我想要生成線狀視圖

在我已經從，到，日期和其他一些列的表

我要輸出通過從分組中的行並在DB到

例如數據

from,to,date 
a,b,somedate 
a,c,somedate 
b,a,somedate 

查詢：

SELECT 
    from, to, date 
FROM 
    data 
GROUP BY 
    from, to 
ORDER BY 
    date DESC; 

我期望的輸出是這樣的：（其中從和組合在一起）

a,b,somedate 
a,c,somedate 

(b,a,somedate not shows because its in the a,b group) 

但它沒有..

總的想法是有一個消息查看「用戶「.. 其中名單是由收件人，日期（不通過消息）排序...

Answer 1

如果你想爲每(from, to)組合一行返回：

SELECT one, two, MIN(somedate) 
FROM 
(SELECT `from` AS one, `to` AS two, somedate 
    FROM data 
    WHERE `from` <= `to` 
UNION ALL 
    SELECT `to`, `from`, somedate 
    FROM data 
    WHERE `from` > `to` 
) AS tmp 
GROUP BY one 
     , two 
ORDER BY one 
     , two 

或者，如果你希望所有記錄：

SELECT one, two, somedate 
FROM 
(SELECT `from` AS one, `to` AS two, somedate 
    FROM data 
    WHERE `from` <= `to` 
UNION ALL 
    SELECT `to`, `from`, somedate 
    FROM data 
    WHERE `from` > `to` 
) AS tmp 
ORDER BY one 
     , two