with orders  as (
  select 1 as article, 10 as qty, 10 as due_days from dual union all
  select 1 as article, 10 as qty, 15 as due_days from dual union all
  select 2 as article, 20 as qty, 10 as due_days from dual union all
  select 2 as article, 10 as qty, 15 as due_days from dual union all
  select 2 as article,  5 as qty, 15 as due_days from dual union all
  select 3 as article, 10 as qty, 30 as due_days from dual
), sklad as (
  select 1 as article,  5 as qty, to_date('01.08.2019', 'dd.mm.yyyy') as date_prod, to_date('20.08.2019', 'dd.mm.yyyy') as bbf  from dual union all
  select 1 as article, 20 as qty, to_date('05.08.2019', 'dd.mm.yyyy') as date_prod, to_date('25.08.2019', 'dd.mm.yyyy') as bbf from dual union all
  select 2 as article,  5 as qty, to_date('01.08.2019', 'dd.mm.yyyy') as date_prod, to_date('20.08.2019', 'dd.mm.yyyy') as bbf from dual union all
  select 2 as article, 15 as qty, to_date('05.08.2019', 'dd.mm.yyyy') as date_prod, to_date('25.08.2019', 'dd.mm.yyyy') as bbf from dual
)

select 
      o.article, 
      o.due_days, 
      sum(o.qty) z_qty,
      trunc(sysdate) + o.due_days - 
      (
         (select s.bbf - date_prod -- эта выборка делается из справочника (срок годности товара в днях)
          from sklad s
          where s.article = o.article and rownum = 1)
       ) as min_date -- минимальная дата производства которую можно отгрузить
from 
      orders o
group by o.article, o.due_days
order by o.article