with TABLE_A(code, dae) as
(
select 1, '아시아' from dual union all
select 2, '유럽' from dual union all
select 3, '북미' from dual
),
TABLE_B(code, country) as
(
select 1, '한국' from dual union all
select 1, '일본' from dual union all
select 1, '중국' from dual union all
select 2, '프랑스' from dual union all
select 2, '독일' from dual union all
select 3, '미국' from dual union all
select 3, '멕시코' from dual union all
select 3, '캐나다' from dual
) 
select
  decode(t.rowno, 1, t.code) as code,
   t.country,
  decode(t.rowno, 1, t.code || '/') || t.country as txt
from
(
   select
     row_number() over(partition by tb.code order by country desc) rowno,
     tb.*
   from   
     table_a ta
     inner join table_b tb on tb.code = ta.code
) t
order by
  t.code, t.rowno;