SQL - 如果Else裏面的返回值？

SELECT 

subj.SubjectID   AS [ID], 
subj.SubjectDescription AS [Subject], 
enrol.StuSubjEnrolmentID AS [IsEnrol] 


FROM [PATHWAYS].[Subjects] AS [subj] 

LEFT JOIN 
[STUDENT].[StuSubjEnrolment] AS [enrol] 
ON subj.SubjectID = enrol.SubjectID 

LEFT JOIN 
[STUDENT].[Student] AS [stu] 
ON enrol.StuID = stu.StuID 
AND stu.StuID = @stuID

傢伙嗨，任何人都可以請指導我這個？先謝謝你。我對此很無能。SQL - 如果Else裏面的返回值？

我怎麼能寫的方式，這種說法....

當IsEnrol是不爲空，則返回0否則返回1？我想那個特定的列，只顯示1或0

來源

2016-04-03 DriLLFreAK100

嘗試使用CASE表達式 – Dejan

你希望每個IsEnrol行爲1或0，如果它是NULL /非NULL？存儲過程如何進入這個過程？ – iliketocode

[如何在SQL SELECT中執行IF ... THEN]可能的重複？（http://stackoverflow.com/questions/63447/how-to-perform-an-if-then-in-an-sql - 請選擇） –

試試這個

SELECT 

subj.SubjectID   AS [ID], 
subj.SubjectDescription AS [Subject], 
CASE WHEN enrol.StuSubjEnrolmentID is not null then 0 else 1 end as AS [IsEnrol] 

FROM [PATHWAYS].[Subjects] AS [subj] 
LEFT JOIN [STUDENT].[StuSubjEnrolment] AS [enrol] 
ON subj.SubjectID = enrol.SubjectID 
LEFT JOIN [STUDENT].[Student] AS [stu] 
ON enrol.StuID = stu.StuID 
AND stu.StuID = @stuID

來源

2016-04-03 17:46:20 Dejan

非常感謝。這就是答案：D – DriLLFreAK100

假設你正在使用SQL Server 2012或更高版本，可以使用IIF功能 -

SELECT 

subj.SubjectID   AS [ID], 
subj.SubjectDescription AS [Subject], 
iif(enrol.StuSubjEnrolmentID is null,1,0) AS [IsEnrol] 


FROM [PATHWAYS].[Subjects] AS [subj] 

LEFT JOIN 
[STUDENT].[StuSubjEnrolment] AS [enrol] 
ON subj.SubjectID = enrol.SubjectID 

LEFT JOIN 
[STUDENT].[Student] AS [stu] 
ON enrol.StuID = stu.StuID 
AND stu.StuID = @stuID

如果您正在使用早於2012年的SQL Server版本，那麼@ dejan87的帖子中的Case聲明方法將是最佳解決方案。

來源

2016-04-03 17:52:51 iliketocode

SQL - 如果Else裏面的返回值？

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