Ranking in a funny way

Question

Date     Category     Rank by Date     Rank by Category     RANKING
01/01/2010     A     1          1          1
05/02/2010     A     2          2          1
18/02/2010     A     3          3          1
30/06/2010     A     4          4          1
12/07/2010     B     5          1          2
20/07/2010     B     6          2          2
29/08/2010     B     7          3          2
31/08/2010     B     8          4          2
02/09/2010     B     9          5          2
30/11/2010     A     10          5          3
02/12/2010     A     11          6          3
04/12/2010     C     12          1          4
06/12/2010     C     13          2          4
By using the ranking function, I can obtain the ranking by date and category easily (with the use of partition). However, I have problem in getting the output for the last column (RANKING). Can somebody find a solution for this?

Answer 1

May be this
with t
as
select to_date('01/01/2010','dd/mm/rrrr') dt, 'A' category from dual union all
select to_date('05/02/2010','dd/mm/rrrr'), 'A' from dual union all
select to_date('18/02/2010','dd/mm/rrrr'), 'A' from dual union all
select to_date('30/06/2010','dd/mm/rrrr'), 'A' from dual union all
select to_date('12/07/2010','dd/mm/rrrr'), 'B' from dual union all
select to_date('20/07/2010','dd/mm/rrrr'), 'B' from dual union all
select to_date('29/08/2010','dd/mm/rrrr'), 'B' from dual union all
select to_date('31/08/2010','dd/mm/rrrr'), 'B' from dual union all
select to_date('02/09/2010','dd/mm/rrrr'), 'B' from dual union all
select to_date('30/11/2010','dd/mm/rrrr'), 'A' from dual union all
select to_date('02/12/2010','dd/mm/rrrr'), 'A' from dual union all
select to_date('04/12/2010','dd/mm/rrrr'), 'C' from dual union all
select to_date('06/12/2010','dd/mm/rrrr'), 'C' from dual
temp as
select dt, category, last_value(x ignore nulls) over (order by dt) x
  from (
         select dt, category, decode(lag(category) over(order by dt), category, null, rownum) x
           from t
select temp.dt, temp.category, temp1.rno
  from temp,
       (select x, rownum rno
          from (select distinct x
                  from temp
                 order by to_number(x))) temp1
where temp.x = temp1.x
order by 1