sql - 在 SQL 中从字符串变量和时间变量（例如术语）创建新变量

Question

我正在尝试根据来自两个不同表的另外两个变量来派生一个变量。我想知道一个学生在他们结束的队列学期（即他们离开大学的学期，无论是否毕业）的课程。我认为合并可能是错误的功能。这是我的代码：

select distinct s.colleagueId,st.term, 
coalesce(EndProgram.EndProgram) EndProgram
from tbl_studentTerms st 
inner join dbo.tbl_Terms t
  on st.term = t.term
  inner join
   tbl_students s
   on st.colleagueId = s.colleagueId 

-- 结束队列计划

left join (
select st.activeProgram as EndProgram
from tbl_studentTerms st
inner join tbl_students s
on s.colleagueId=st.colleagueId
where st.term = s.endingCohort) EndProgram
on EndProgram.colleagueId = s.colleagueId

Answer 1

End Cohort Program 部分的最后一行，您将加入“on EndProgram.colleagueId = s.colleagueId” - 但是，您标记为 EndProgram 的 select 语句不会返回 ColleagueID 列，因此您无法加入它. 如果添加它，您可能会解决该特定问题：

left join (
select st.activeProgram as EndProgram,
s.colleagueId as ColleagueID
from tbl_studentTerms st
inner join tbl_students s
on s.colleagueId=st.colleagueId
where st.term = s.endingCohort) EndProgram
on EndProgram.colleagueId = s.colleagueId