Question

我需要做一个case语句，对结果进行分组并在SQL查询中计算结果。到目前为止，我已经做到了这一点，但不太确定如何让它正常工作：

SELECT 'OS' = 
    CASE
        WHEN OS.Info LIKE 'AIX %' THEN 'Unix'
        WHEN OS.Info LIKE 'LINUX%' THEN 'Unix'
    END, COUNT( 'OS' )
FROM Asset A (NOLOCK)
LEFT JOIN Asset_IP AIP (NOLOCK) ON A.AssetID = AIP.AssetID AND AIP.LastUpdateDate = (SELECT MAX( Asset_IP.LastUpdateDate ) FROM Asset_IP (NOLOCK) WHERE A.AssetID = Asset_IP.AssetID)
LEFT JOIN Asset_IP_OS AIPOS (NOLOCK) ON AIP.AssetIPID = AIPOS.AssetIPID
LEFT JOIN OSNav OS (NOLOCK) ON AIPOS.OSNavID = OS.OSNavID
GROUP BY OS.Info
ORDER BY OS.Info

操作系统可能会出现在AIX 7.0或AIX 7.2或Linux 2.3或Windows 7或Solaris 10上。所有基于Unix的操作系统都必须在Unix下进行计数等...我希望它能显示这样的东西：

OS      Count
Unix    200
Windows 1200

Answer 1

您需要在CASE中使用Group By语句，或使用派生表来使用OS中的别名group by。由于我们已移除OS.Info中的group by，因此我们无法在OS.Info中使用order by。在OS

中使用别名Order by

SELECT OS = CASE
              WHEN OS.Info LIKE 'AIX %'
                    OR OS.Info LIKE 'LINUX%' THEN 'Unix'
              ELSE 'Others' --default
            END,
       Count(OS.Info)
FROM   Asset A (NOLOCK)
       LEFT JOIN Asset_IP AIP (NOLOCK)
              ON A.AssetID = AIP.AssetID
                 AND AIP.LastUpdateDate = (SELECT Max(Asset_IP.LastUpdateDate)
                                           FROM   Asset_IP (NOLOCK)
                                           WHERE  A.AssetID = Asset_IP.AssetID)
       LEFT JOIN Asset_IP_OS AIPOS (NOLOCK)
              ON AIP.AssetIPID = AIPOS.AssetIPID
       LEFT JOIN OSNav OS (NOLOCK)
              ON AIPOS.OSNavID = OS.OSNavID
GROUP  BY CASE
            WHEN OS.Info LIKE 'AIX %'
                  OR OS.Info LIKE 'LINUX%' THEN 'Unix'
            ELSE 'Others'
          END
ORDER  BY OS

注意：我已添加else语句，以便在表达式不满意时避免NULL's。

SQL Case语句COUNT

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