Question

查询：

select machinename, StatusCode, max(size) as size, statusID
from machine where MachineID In( '33','22') and StatusCode = 166 
group by machinename, StatusCode, statusID
order by max(size) DESC

结果：

   machinename  StatusCode  size statusID
    -----------  ----------  ---- --------
    test1        166         50       1
    test1        166         25       2
    test2        166         75       3
    test2        166         48       4

要求：

我需要为每台机器只显示一个条目。我必须通过获取两个条目之间的最大大小值来完成此操作，如上所示。对于test1我有两个尺寸50和25我必须显示有50的行而忽略有25的行。

由于

期望的结果：

 machinename  StatusCode  size statusID
    -----------  ----------  ---- --------
    test1        166         50       1  
    test2        166         75       3

Answer 1

SELECT machinename, StatusCode, size, statusID
FROM (
    SELECT
        machinename,
        StatusCode,
        size,
        statusID,
        ROW_NUMBER() OVER (PARTITION BY MachineID ORDER BY size DESC) AS rn
    FROM machine
    WHERE MachineID IN ('33','22')
    AND StatusCode = 166 
) T1
WHERE rn = 1
ORDER BY size DESC

Answer 2

“旧”SQL Server的三种解决方案 s ：

SELECT  *
FROM    TestData a
WHERE   a.Size >= ALL(SELECT b.Size FROM TestData b WHERE b.MachineName=a.MachineName);

SELECT  *
FROM    TestData a
WHERE   a.Size = (SELECT MAX(b.Size) FROM TestData b WHERE b.MachineName=a.MachineName);

SELECT  a.*
FROM    TestData a
JOIN    (SELECT MachineName, MAX(Size) MaxSize FROM TestData GROUP BY MachineName) b 
ON      a.MachineName=b.MachineName 
AND     a.Size=b.MaxSize;

结果：

MachineName StatusCode  Size        StatusID
----------- ----------- ----------- -----------
test2       166         75          3
test1       166         50          1

警告：如果有很多行具有相同的机器最大值，则所有这些查询都会显示这些行。

查询从多行获取一个条目

2 个答案: