SQL多個組 - 可能嗎？

Question

我有這個形式的查詢：

SELECT e.date, SUM(e.size) as bytes 
FROM entries AS e 
GROUP BY e.date 
ORDER BY bytes DESC 

，我有一個名爲客戶端柱，它是由靜態值（0,1,2,3），所以我希望得到這樣的：

SELECT e.date, SUM(e.size) as bytes 
FROM entries AS e 
WHERE e.client = 0 
GROUP BY e.date 
ORDER BY bytes DESC 

重複爲每個客戶端類型，但在一個單一的查詢來獲取每一個客戶端類型彙總尺寸的結果：

DATE | CLI0-SIZE | CLI1-SIZE | CLI2-SIZE | CLI3-SIZE 
2010-11-11  113   344   435   155 

Answer 1

你可以試試這個

SELECT e.date, 
    SUM(CASE WHEN e.client = 0 THEN e.size ELSE 0 END) as CLI0-SIZE, 
    SUM(CASE WHEN e.client = 1 THEN e.size ELSE 0 END) as CLI1-SIZE, 
    SUM(CASE WHEN e.client = 2 THEN e.size ELSE 0 END) as CLI2-SIZE, 
    SUM(CASE WHEN e.client = 3 THEN e.size ELSE 0 END) as CLI3-SIZE 
FROM entries AS e 
GROUP BY e.date 

Answer 2

關係數據庫管理系統：Microsoft SQL Server的

這將返回以下佈局：

date | client | bytes 
2010-11-11 | 2 | 435 
2010-11-11 | 1 | 344 
2010-11-11 | 3 | 155 
2010-11-11 | 0 | 113 

這將組的所有客戶端類型，而不僅僅是0,1,2,3 - 我想你想要這個。

SELECT 
    e.date, 
    e.client, 
    SUM(e.size) AS bytes 
FROM 
    entries AS e 
GROUP BY 
    e.date, 
    e.client 
ORDER BY 
    bytes DESC 

然後，您可以在桌子上執行數據透視。