带CASE的SQL连接条件

我有一个查询，我正在使用它将多个列连接到一个列，但是我得到了“临近学年的错误语法”。有什么想法吗？我不太确定如何在join中结束这个案例

select distinct 
    bb.pk1 as 'LearnSourceKey',
    sc.pk1 as 'SISSourceKey',
    row_number () over (partition by bb.pk1 order by sc.SISCourseKey) as 'RowRank'
from
    Source.SISCourse sc
    left join source.SISTerm st on sc.TermSourceKey=st.SISTermKey
    inner join Source.COURSE_MAIN bb
        on bb.batch_uid = substring(CatalogNumber, 1, (len(CatalogNumber) - 1)) + 
            case 
                when st.TermDescription='Semester 1' 
                then 'SEM-1'  + '_' + st.AcademicYear   

---

Case语句应该有结束表达式

select distinct 
    bb.pk1 as 'LearnSourceKey',
    sc.pk1 as 'SISSourceKey',
    row_number () over (partition by bb.pk1 order by sc.SISCourseKey) as 'RowRank'
from
Source.SISCourse sc
left join source.SISTerm st on sc.TermSourceKey=st.SISTermKey
inner join Source.COURSE_MAIN bb 
      on bb.batch_uid = substring(CatalogNumber,  1, (len(CatalogNumber) - 1)) + 
         case 
            when st.TermDescription='Semester 1' 
            then  'SEM-1'  + '_' + st.AcademicYear 
         end 

---

这是您的查询，基本上是：

select distinct bb.pk1 as LearnSourceKey,
       sc.pk1 as SISSourceKey,
       row_number () over (partition by bb.pk1 order by sc.SISCourseKey) as RowRank
from Source.SISCourse sc left join
     source.SISTerm st
     on sc.TermSourceKey = st.SISTermKey inner join
     Source.COURSE_MAIN bb
     on bb.batch_uid = (left(CatalogNumber, len(CatalogNumber) - 1) + 
                        (case when st.TermDescription = 'Semester 1' then 'SEM-1'  + '_' + st.AcademicYear end) 
                       );

您的

案例

没有

else

子句。因此，当条件满足时，任何不满足条件的内容都将为NULL。这意味着您可以将其简化为：

select distinct bb.pk1 as LearnSourceKey,
       sc.pk1 as SISSourceKey,
       row_number () over (partition by bb.pk1 order by sc.SISCourseKey) as RowRank
from Source.SISCourse sc left join
     source.SISTerm st
     on sc.TermSourceKey = st.SISTermKey inner join
     Source.COURSE_MAIN bb
     on st.TermDescription = 'Semester 1' and
        bb.batch_uid = (left(CatalogNumber, len(CatalogNumber) - 1) + 
                        st.AcademicYear
                       );

---

这（与原始查询一样）假设

st.AcademicYear

是一个字符串。

您没有

结束
case
表达式。您应该提供示例数据和所需结果。