Есть таблица

with a as (
select 'a' as fio,  '116-935-936 86' as inn
from dual connect by level < 4
union all
select 'b' as fio,  '046-944-605 86' as inn
from dual connect by level < 4
union all
select 'c' as fio,  '046-947-949 18' as inn
from dual connect by level < 4
)
select * from a

Надо:
1. Сгруппировать по фио и инн.
2. После каждой такой группы вывести пустую строчку.

Помогите. 3 дня голову ломаю