Query to retrieve next valid record

Question

Hi All
I have a strange requirement to write a query/logic to achieve the following. I have a table which has a date column and a field which signifies whether it is a valid date or not
Date Valid
11/01/2010 Y
12/01/2010 N
13/01/2010 N
17/02/2010 Y
15/03/2010 N
11/04/2010 Y
21/06/2010 Y
18/08/2010 N
14/09/2010 N
17/10/2010 Y
If a particular date is not valid, I need to output the next valid date. So someting like
Date Valid     Valid date
11/01/2010 Y          11/01/2010
12/01/2010 N          17/02/2010
13/01/2010 N          17/02/2010
17/02/2010 Y          17/02/2010
15/03/2010 N          11/04/2010
11/04/2010 Y          11/04/2010
21/06/2010 Y          21/06/2010
18/08/2010 N          17/10/2010
14/09/2010 N          17/10/2010
17/10/2010 Y          17/10/2010
Is this possible in one single query ?
Thanks
Birdy

Answer 1

with t as (
           select to_date('11/01/2010','dd/mm/yyyy') dt,'Y' valid from dual union all
           select to_date('12/01/2010','dd/mm/yyyy'),'N' from dual union all
           select to_date('13/01/2010','dd/mm/yyyy'),'N' from dual union all
           select to_date('17/02/2010','dd/mm/yyyy'),'Y' from dual union all
           select to_date('15/03/2010','dd/mm/yyyy'),'N' from dual union all
           select to_date('11/04/2010','dd/mm/yyyy'),'Y' from dual union all
           select to_date('21/06/2010','dd/mm/yyyy'),'Y' from dual union all
           select to_date('18/08/2010','dd/mm/yyyy'),'N' from dual union all
           select to_date('14/09/2010','dd/mm/yyyy'),'N' from dual union all
           select to_date('17/10/2010','dd/mm/yyyy'),'Y' from dual
select  dt,
        valid,
        min(
            case valid
              when 'Y' then dt
            end
           ) over(order by dt rows between current row and unbounded following) valid_dt
  from  t
  order by dt
DT         V VALID_DT
11/01/2010 Y 11/01/2010
12/01/2010 N 17/02/2010
13/01/2010 N 17/02/2010
17/02/2010 Y 17/02/2010
15/03/2010 N 11/04/2010
11/04/2010 Y 11/04/2010
21/06/2010 Y 21/06/2010
18/08/2010 N 17/10/2010
14/09/2010 N 17/10/2010
17/10/2010 Y 17/10/2010
10 rows selected.
SQL> SY.