Question

我目前正在尝试自学SQL，以便使用我们的Orion系统编写更好的报告，并且我遇到了一个小问题。我想生成一个包含Windows机器和Linux机器数量的报告。这是我目前的代码。

   SELECT OperatingSystem, Count(OperatingSystem) AS TotalMachines
    FROM Machines
    Where
    (
    (OperatingSystem LIKE '%Windows%') OR 
    (OperatingSystem LIKE '%Linux%')
    )
    GROUP BY OperatingSystem

我得到的回报就是这个

Red Hat Enterprise Linux            20
Novell SUSE Linux Enterprise        17
Debian Linux                         5
Windows Server 2008 (32-bit)        11
Windows Server 2008 R2 (32-bit)     49
Windows Server 2008 (64-bit)        33
Windows Server 2008 R2 (64-bits)    16
Windows Server 2003 (32-bit)        35

是否可以将所有不同的Linux操作系统组合成一个名为Linux的行，并将所有Windows操作系统组合成一个名为Windows的SQL查询行？

Answer 1

是。您想在case子句中使用group by：

SELECT (case when OperatingSystem LIKE '%Windows%' then 'Windows'
            when OperatingSystem LIKE '%Linux%' then 'Linux'
       end) as WhichOs, Count(*) AS TotalMachines
FROM Machines
Where (OperatingSystem LIKE '%Windows%') OR 
      (OperatingSystem LIKE '%Linux%')
GROUP BY (case when OperatingSystem LIKE '%Windows%' then 'Windows'
               when OperatingSystem LIKE '%Linux%' then 'Linux
          end);

编辑：

以上内容应该有效（请注意select和group by中的相同表达式。也许这样可行：

SELECT WhichOs, Count(*) AS TotalMachines
FROM (SELECT m.*,
            (case when OperatingSystem LIKE '%Windows%' then 'Windows'
                  when OperatingSystem LIKE '%Linux%' then 'Linux'
             end) as WhichOs
      FROM Machines m
     ) m
Where (OperatingSystem LIKE '%Windows%') OR 
      (OperatingSystem LIKE '%Linux%')
GROUP BY WhichOs;

Answer 2

尝试这样的事情：

SELECT 
  case 
    when OperatingSystem like '%Windows%' then 'Windows'
    when OperatingSystem like '%Linux%' then 'Linux'
    else 'Other'
 end as Operating_System
, Count(OperatingSystem) AS TotalMachines
FROM Machines
Where
(
   (OperatingSystem LIKE '%Windows%') OR 
   (OperatingSystem LIKE '%Linux%')
)
GROUP BY 
  OperatingSystem
, case 
    when OperatingSystem like '%Windows%' then 'Windows'
    when OperatingSystem like '%Linux%' then 'Linux'
    else 'Other'
end

Answer 3

要解决此类问题，我更倾向于使用union case，因为它可以帮助您以后轻松扩展查询：

select OSType, count(*) as TotalMachines
from (
    SELECT 'Linux' as OSType FROM Machines WHERE OperatingSystem LIKE '%Linux%'
    UNION ALL
    SELECT 'Windows' as OSType FROM Machines WHERE OperatingSystem LIKE '%Windows%'
) as subquery
GROUP BY OSType

无论如何，请检查两种变体并选择最快的

合并SQL计数结果

3 个答案: