Question

SELECT * FROM 
    (SELECT sum(DATA.dayMB) as "totaldayMb", 
      data.customerid 
    FROM DATA,customer 
    WHERE data.customerid=customer.customerid 
      AND customer.projectid='"+ ProjectID +"' 
      AND customer.stateid='"+ StateID +"' 
      AND DATA.dataDate between '"+ initialDate +"' 
      AND '"+ finalDate +"' 
      AND data.upstatus='"+upstatus+"' 
    GROUP BY data.customerid 
    ORDER BY sum(DATA.dayMB) desc 
    ) 
    WHERE ROWNUM <= 25 

在此查詢我想選擇25個用戶，誰使用最大數據B/W解散日期。我使用的MySQL。

Answer 1

SELECT * FROM 
    (SELECT sum(DATA.dayMB) as "totaldayMb", 
      data.customerid 
    FROM DATA,customer 
    WHERE data.customerid=customer.customerid 
      AND customer.projectid='"+ ProjectID +"' 
      AND customer.stateid='"+ StateID +"' 
      AND DATA.dataDate between '"+ initialDate +"' 
      AND '"+ finalDate +"' 
      AND data.upstatus='"+upstatus+"' 
    GROUP BY data.customerid 
    ORDER BY sum(DATA.dayMB) desc 
    ) AS baseview 
    LIMIT 25 

心靈的AS baseview在最後，但一一行。

Ofcourse這是有道理的，只有當內部查詢是在查詢緩存中。如果沒有，只是用

SELECT sum(DATA.dayMB) as "totaldayMb", 
      data.customerid 
FROM DATA,customer 
WHERE data.customerid=customer.customerid 
      AND customer.projectid='"+ ProjectID +"' 
      AND customer.stateid='"+ StateID +"' 
      AND DATA.dataDate between '"+ initialDate +"' 
      AND '"+ finalDate +"' 
      AND data.upstatus='"+upstatus+"' 
GROUP BY data.customerid 
ORDER BY sum(DATA.dayMB) desc 
LIMIT 25 

Answer 2

使用LIMIT運算符（docu @ MySQL）限制返回的行數，而不是使用附加的查詢。

這樣你也可以避免你的錯誤。

SELECT sum(DATA.dayMB) as "totaldayMb", 
     data.customerid 
FROM DATA,customer 
WHERE data.customerid=customer.customerid 
     AND customer.projectid='"+ ProjectID +"' 
     AND customer.stateid='"+ StateID +"' 
     AND DATA.dataDate between '"+ initialDate +"' 
     AND '"+ finalDate +"' 
     AND data.upstatus='"+upstatus+"' 
GROUP BY data.customerid 
ORDER BY sum(DATA.dayMB) desc 
LIMIT 0,25