Problem with Fiscal weeks

Question

Hi,
I have to write a query which should fetch data for the last 6 fiscal weeks from the data from which it is run.
eg
SELECT TO_CHAR(SYSDATE,'YYYYIW')-6 FROM DUAL
The above query would give me the last 6th fiscal week from the current date, but this query fails when the date lies in the first 6 fiscal weeks, it would return something like 200595 which should be 200546. The problem is that the number of the fiscal weeks for a year are not fixed. it might be 52, 53 or 54 also.
Is there any function existing in oracle that would handle the above problem? if not can ayone help me to find a workaround for that.
Thanks in advance
Ramesh

Answer 1

Is it a problem with week starting end of year and ending at the begining of the following year ?
If yes, you maybe need to work with WW instead of IW, and try something like :
SQL> exec :dt:='02062006'
PL/SQL procedure successfully completed.
SQL> ed
Wrote file afiedt.buf
  1  select to_char(to_date(:dt,'DDMMYYYY'),'YYYYWW') "WEEK",
  2         case when to_char(to_date(:dt,'DDMMYYYY'),'WW') -6 > 0
  3              then to_char(to_date(:dt,'DDMMYYYY'),'YYYYWW') -6
  4              else to_char(last_day(trunc(to_date(:dt,'DDMMYYYY'),'YYYY')-1),'YYYYWW')
  5                   + (to_char(to_date(:dt,'DDMMYYYY'),'WW') -6) end WEEK_MIN_6
  6* from dual
SQL> /
WEEK   WEEK_MIN_6
200622     200616
SQL> exec :dt:='05012005'
PL/SQL procedure successfully completed.
SQL> select to_char(to_date(:dt,'DDMMYYYY'),'YYYYWW') "WEEK",
  2         case when to_char(to_date(:dt,'DDMMYYYY'),'WW') -6 > 0
  3              then to_char(to_date(:dt,'DDMMYYYY'),'YYYYWW') -6
  4              else to_char(last_day(trunc(to_date(:dt,'DDMMYYYY'),'YYYY')-1),'YYYYWW')
  5                   + (to_char(to_date(:dt,'DDMMYYYY'),'WW') -6) end WEEK_MIN_6
  6  from dual
  7  /
WEEK   WEEK_MIN_6
200501     200448
SQL> Nicolas.