sql - Not a single-group group function while using case when statements -

in query trying use case when keywords. have check 3 conditions there. getting not single-group group function error. syntax error in query? please guide.

query

select           case when dist_type_id in (5033,5034,5035,5036)          min (b2b_start_dt +nvl(access_lead_days,0))         else               case when max(overridden) = 0               nvl (min (src_start_dt), min (b2b_start_dt))               else max(b2b_start_dt) end          end start_date      prog_access_movie_v             trunc(sysdate) between b2b_start_dt , b2b_end_dt               , (user_id not null or group_id not null)                 , dist_type_id in (5034) , prog_id = (432899) 

this select:

select  (case when dist_type_id in (5033, 5034, 5035, 5036)                min(b2b_start_dt + nvl(access_lead_days, 0))               else (case when max(overridden) = 0                           nvl(min(src_start_dt), min(b2b_start_dt))                           else max(b2b_start_dt)                     end)          end) start_date  

in terms of aggregation, fine except condition on dist_type_id. if had:

select  (case when max(dist_type_id) in (5033, 5034, 5035, 5036)                min(b2b_start_dt + nvl(access_lead_days, 0))               else (case when max(overridden) = 0                           nvl(min(src_start_dt), min(b2b_start_dt))                           else max(b2b_start_dt)                     end)          end) start_date  

or:

select  (case when sum(case when dist_type_id in (5033, 5034, 5035, 5036) 1 else 0 end) > 0               min(b2b_start_dt + nvl(access_lead_days, 0))               else (case when max(overridden) = 0                           nvl(min(src_start_dt), min(b2b_start_dt))                           else max(b2b_start_dt)                     end)          end) start_date  

or myriad of other possibilities, query should parse , execute.