我正在编写一个查询以从两个表中检索数据。该表有这样的数据:具有多个SQL时出现空值
表1:
StudentId Studentname
---------------------
1 test
2 test1
表2:
StudentId Assignmentstatus date
--------------------------------------
1 0 01/01/2014
1 1 02/01/2014
状态1意味着分配提交,2种手段验证后返回。
虽然加入表
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.
它用于StudentId 2也返回1。
什么是你想去做? – DavidG 2014-11-03 10:53:25
你想做什么? – 2014-11-03 10:53:31
@DavidG会将“AssignmentSubmitted”设置为零,并studentid 1.现在它返回一个studentid 2. – user2395176 2014-11-03 10:55:57