create table temp_22112017_inn
as 
select 1 inn from dual
union
select 2 from dual
union
select 3 from dual
/
create table temp_22112017_inn_sum
as 
select 1 inn, 500 summ from dual
union
select 2, 600 summ from dual
union
select 3, 300 summ from dual
/--Ïî÷åìó òóò íå âîçíèêëî îøèáêè, êàê ýòî áûëî â 11ñ
select inn, summ from 
(select a.inn, summ 
from 
  (select distinct inn from temp_22112017_inn) a
   left join (select inn, sum(summ) summ from temp_22112017_inn_sum b group by inn)b on a.inn = b.inn)
group by inn
/
/*
drop table temp_22112017_inn;
drop table temp_22112017_inn_sum;

oracle database 12c enterprise edition release 12.1.0.2.0 - 64bit production
*/