如何在案例陈述中使用join

Question

下面的代码不起作用。 我想拉出相应PACKAGE的BatchHorizo​​n。 我不能直接使用“ then BatchHorizo​​n”，因为batchhorizo​​n位于子查询中。

Case When PACKAGE IN (SELECT DISTINCT PACKAGE
                      FROM BATCHINGWINDOW AS A
                     ) 
     Then (SELECT  BatchHorizon
           FROM BATCHINGWINDOW AS B 
           WHERE B.PACKAGE = A.PACKAGE
         )
     else 3
 end

Answer 1

select 

Case When O.PACKAGE IN (SELECT PACKAGE
                      FROM BATCHINGWINDOW  
                     ) 
     Then (SELECT  DISTINCT BatchHorizon
           FROM BATCHINGWINDOW AS B 
           WHERE B.PACKAGE = O.PACKAGE
         )
     else 3
 end pack
 from table O