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 

在此查询我想选择25个用户，谁使用最大数据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 

心灵的AS baseview在最后，但一一行。

Ofcourse这是有道理的，只有当内部查询是在查询缓存中。如果没有，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运算符（docu @ MySQL）限制返回的行数，而不是使用附加的查询。

这样你也可以避免你的错误。

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