Question

以下Case语句无法正常工作 - 将所有结果生成为＆＃39; i＆＃39; （声明中的＆＃39; Else＆＃39;部分）。如果我注释掉 Else 部分代码可以正常工作，那么在符合条件的情况下产生NULL。任何想法为什么会这样？ ELSE不受支持吗？我确定我在Case声明中使用了Else（但从未使用和）？

SELECT 
        EN,
        (First_Name + ' ' + Last_Name) as Name,

        First_Aid =MAX(CASE
            WHEN Course = 'First Aid' 
            and Status = 'Finished'
            and Course_Start_Date > DATEADD(day, -1095, GETDATE())
            THEN 'F'
            ELSE 'i'
            END),

        Manual_Handling =MAX(CASE
            WHEN Course = 'Manual Handling' 
            and Status = 'Finished'
            and Course_Start_Date > DATEADD(day, -1095, GETDATE())
            THEN 'F'
            ELSE 'i'
            END),

        Fire_Safety =MAX(CASE
            WHEN Course = 'Fire Safety' 
            and Status = 'Finished'
            and Course_Start_Date > DATEADD(day, -1095, GETDATE())
            THEN 'F'
            ELSE 'i'
            END)
into MyTraining
FROM Learning_History

Group By EN,First_Name, Last_Name

Answer 1

正如GSerg评论的那样，你问的是错误的。您可能希望使用这样的查询：

Fire_Safety =MAX(CASE
WHEN Course = 'Fire Safety' 
and Status = 'Finished'
and Course_Start_Date > DATEADD(day, -1095, GETDATE())
THEN Course_Start_Date
ELSE null
END)

这将为您提供最近的消防安全课程，或null如果没有满足条件的话。然后，如果需要，您可以在case附近另外max根据返回的值返回T或F或任何您想要的内容。或者不是，在任何一种情况下都不清楚你想要发生什么:)

Answer 2

我认为你想在聚合之外将作业拉到I和F.这是一种方法：

SELECT EN,
       (First_Name + ' ' + Last_Name) as Name,
       (CASE WHEN SUM(CASE WHEN Course = 'First Aid' and Status = 'Finished' and Course_Start_Date > DATEADD(day, -1095, GETDATE())
                           THEN 1 ELSE 0 END) > 0
             THEN 'F' ELSE 'I'
        END) as First_Aid,
       (CASE WHEN SUM(CASE WHEN course = 'Manual Handling' and Status = 'Finished' and Course_Start_Date > DATEADD(day, -1095, GETDATE()) > 0
                          THEN 1 ELSE 0 END) > 0
             THEN 'F' ELSE 'I'
        END) as Manual_Handling,
       (CASE WHEN SUM(CASE WHEN Course = 'Fire Safety' and Status = 'Finished' and Course_Start_Date > DATEADD(day, -1095, GETDATE())
                               THEN 1 ELSE 0 END) > 0
            THEN 'F'
            ELSE 'i'
        END) as Fire_Safety
into MyTraining
FROM Learning_History
Group By EN, First_Name, Last_Name

SQL案例声明不适用于＆＃39; Else＆＃39;

2 个答案: