dummy row를 생성 한후 b에대해 catesian join을 함으로서 해당 결과를 얻을수 있습니다.

with
a
as
( select 1 id , 'AAA' value from dual union all
  select 2, 'BBB' from dual union all
  select 3, 'CCC' from dual
)
,
b
as
( select 1 id , 2 rowvalue from dual union all
  select 2, 3 from dual
)
,
dummy
as
( select rownum  dup
  from dual
  connect by level <= (select max(rowvalue) from b)  )
select value
from
  a
  join b on a.id = b.id
    join dummy on dummy.dup <= b.rowvalue
/