Challenge 6

insert into t_rand_numbers
with numbers(id, n) as (
  select level, round(999 * dbms_random.value(),0)
  connect by level <= 1000000
)
select * from numbers ;

with
quantities(n,times) as (
  select value, count(value) as nn from t_rand_numbers
  group by value
)
select * from quantities q
where not exists(select 1 from quantities q1 where q1.times > q.times)
;