我正在編寫一個查詢以從兩個表中檢索數據。該表有這樣的數據:具有多個SQL時出現空值
表1:
StudentId Studentname
---------------------
1 test
2 test1
表2:
StudentId Assignmentstatus date
--------------------------------------
1 0 01/01/2014
1 1 02/01/2014
狀態1意味着分配提交,2種手段驗證後返回。
雖然加入表
select
student.StudentId, student.Studentname,
case (select top 1 Assignmentstatus
from Assignment
where Assignment.StudentId = student.StudentId
order by date desc) when 0 then 1 else 0 end as AssignmentSubmitted
from
student
left join
Assignment on Assignment.studentId = Student.StudentId.
它用於StudentId 2也返回1。
什麼是你想去做? – DavidG 2014-11-03 10:53:25
你想做什麼? – 2014-11-03 10:53:31
@DavidG會將「AssignmentSubmitted」設置爲零,並studentid 1.現在它返回一個studentid 2. – user2395176 2014-11-03 10:55:57