Correct my query.

Question

Hi gurus,
I am in need of correction of my query to get the correct output.
The table structure and data is as follows:
create table sample_pid (
pid char(1),
asof date,
edf number
select * from table sample_pid;
     PID     ASOF     EDF
     A     29/08/2011     0.1
     A     31/07/2011     0.2
     B     21/08/2011     0.3
     B     31/07/2011     0.4
     C     31/07/2011     0.5
     D     15/07/2011     0.6
     D     30/06/2011     0.7
I have to make a list of PIDs with date sysdate-1.If there are no records for sysdate-1, then get the previous month's records with date between the last seven days of the month.If there are both sysdate-1 and date between the last seven days of the month records available for a PID, then the sysdate-1 record should only be selected.
The output should be:
PID     ASOF     EDF
A     29/08/2011     0.1
B     31/07/2011     0.4
C     31/07/2011     0.5
As per the requirement, B 21/08/2011 is not selected because it is neither sysdate-1 nor a date between last seven days of the previous month.
Likewise D has not been selected since both the dates of D are neither sysdate-1 nor a date between last seven days of the previous month.
I have written a sql but the result set is wrong.I mean i am not getting the desired output.
select pid, asof, edf
from sample_eid
where
*1=case when asof=to_date('30/08/2011', 'dd/mm/yyyy') - 1 then 1*
when asof between last_day(add_months(to_date('30/08/2011', 'dd/mm/yyyy') - 1, -1)) - 6 and
last_day(add_months(to_date('30/08/2011', 'dd/mm/yyyy') - 1, -1)) then 1 end;
I get as follows which is wrong:
     PID     ASOF          EDF
     A     29/08/2011     0.1
     A     31/07/2011     0.2
     B     31/07/2011     0.4
     C     31/07/2011     0.5
Can anyone help me in this?
Thanks in advance.
Edited by: mythili varada on Sep 6, 2011 11:13 AM

Answer 1

is this what you are looking for ?
SELECT *
  FROM (SELECT pid, asof, edf,
               ROW_NUMBER () OVER (PARTITION BY pid ORDER BY asof DESC) rn
          FROM sample_pid
         WHERE 1 =
                  CASE
                     WHEN asof = TO_DATE ('30/08/2011', 'dd/mm/yyyy') - 1
                        THEN 1
                     WHEN asof
                            BETWEEN   LAST_DAY
                                         (ADD_MONTHS (  TO_DATE ('30/08/2011',
                                                                 'dd/mm/yyyy'
                                                      - 1,
                                                      -1
                                    - 6
                                AND LAST_DAY
                                         (ADD_MONTHS (  TO_DATE ('30/08/2011',
                                                                 'dd/mm/yyyy'
                                                      - 1,
                                                      -1
                        THEN 1
                  END)
WHERE rn = 1