Case In The Group By cluses

Question

I Need To Group By Case having sub query is it possible
select
segment3,
( case when segment3 like '210%' and segment4 in ( select child_m from apps.XXNBE_PAR_PROD) then (select parent_m from apps.XXNBE_PAR_PROD where segment4=child_m) else ' ' end ) AS PC,
sum(br_egp) IN_BR_EGP
from apps.XXNBE_FIN_R7 R7
group by
segment3
,( case when segment3 like '210%' and segment4 in ( select child_m from apps.XXNBE_PAR_PROD) then (select parent_m from apps.XXNBE_PAR_PROD where segment4=child_m) else ' ' end );
It's Returne The Error subquery expressions not allowed here

Answer 1

You cant use sub-queries in group by. Try this
select a.segment3,
       case when a.segment3 like '210%' and
                 b.child_m is not null
            then b.parent_m
    else ' '
       end as pc
  from app.XXNBE_FIN_R7 a
  left
  join apps.XXNBE_PAR_PROD b
    on a.segement4 = b.child_m
group
    by a.segment3,
       case when a.segment3 like '210%' and
                 b.child_m is not null
            then b.parent_m
    else ' '
       end