How to find first and last date of a fiscal week using SQL

Question

Hello,
I want information about FISCAL Week, means a Week based on ISO standard. I know format strings ‘IW’ or ‘IYYY’ gives fiscal week and fiscal year respectively from a given date. But I want to find the first and last date of a fiscal week. Say suppose I have a fiscal week is 2, and fiscal year is 2008, how to find the start and end date of the given fiscal week.
Any kind of help would be greatly appreciable.
Thanks,
Prince

Answer 1

davide gislon wrote:
The following query evaluate the begin of a fisical week, where &year and &week are respectively the year and week you want to calculate.
To evaluate the end of the week you have to add 6.
Note that my database is set to have monday as day number 1 of the week, and sunday as day number 7; if your database settings are different you should modify the query accordingly.
SELECT CASE TO_CHAR(TO_DATE('&year','YYYY'),'D')
WHEN '1' THEN TO_DATE('&year','YYYY')+((&week-1)*7)
WHEN '2' THEN TO_DATE('&year','YYYY')+((&week-1)*7-1)
WHEN '3' THEN TO_DATE('&year','YYYY')+((&week-1)*7-2)
WHEN '4' THEN TO_DATE('&year','YYYY')+((&week-1)*7-3)
WHEN '5' THEN TO_DATE('&year','YYYY')+((&week-1)*7+3)
WHEN '6' THEN TO_DATE('&year','YYYY')+((&week-1)*7+2)
WHEN '7' THEN TO_DATE('&year','YYYY')+((&week-1)*7+1)
END BEGIN_FISICAL_WEEK
FROM DUAL
Hope this is helpful.
Cheers,
Davide
Edited by: davide gislon on 08-Jan-2009 07:19Your query does nothing you say it does. TO_DATE('&year','YYYY') returns first day of the current month for year &year. And the only reason it returns January 1, &year is that we are currently in January:
SQL> select TO_DATE('&year','YYYY') from dual
  2  /
Enter value for year: 2005
old   1: select TO_DATE('&year','YYYY') from dual
new   1: select TO_DATE('2005','YYYY') from dual
TO_DATE('
01-JAN-05
SQL> As soon as we roll into February:
SQL> alter system set fixed_date = '2009-2-1' scope=memory
  2  /
System altered.
SQL> select sysdate from dual
  2  /
SYSDATE
01-FEB-09
SQL> select TO_DATE('&year','YYYY') from dual
  2  /
Enter value for year: 2005
old   1: select TO_DATE('&year','YYYY') from dual
new   1: select TO_DATE('2005','YYYY') from dual
TO_DATE('
01-FEB-05
SQL> alter system set fixed_date = NONE scope=both
  2  /
System altered.
SQL> select sysdate from dual
  2  /
SYSDATE
08-JAN-09
SQL> But even if TO_DATE('&year','YYYY') would always return January 1, &year, or you would fix it to TO_DATE('0101&year','MMDDYYYY') it still would be wrong. ISO week rules are
If January 1 falls on a Friday, Saturday, or Sunday, then the week including January 1 is the last week of the previous year, because most of the days in the week belong to the previous year.
If January 1 falls on a Monday, Tuesday, Wednesday, or Thursday, then the week is the first week of the new year, because most of the days in the week belong to the new year.Therefore, next year:
SQL> DEFINE YEAR=2010
SQL> DEFINE WEEK=1
SQL> ALTER SESSION SET NLS_TERRITORY=GERMANY -- enforce Monday as first day of the week
  2  /
Session altered.
SQL> SET VERIFY OFF
SQL> SELECT CASE TO_CHAR(TO_DATE('0101&&year','MMDDYYYY'),'D')
  2  WHEN '1' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7)
  3  WHEN '2' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7-1)
  4  WHEN '3' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7-2)
  5  WHEN '4' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7-3)
  6  WHEN '5' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7+3)
  7  WHEN '6' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7+2)
  8  WHEN '7' THEN TO_DATE('0101&&year','MMDDYYYY')+((&&week-1)*7+1)
  9  END BEGIN_FISICAL_WEEK
10  FROM DUAL
11  /
BEGIN_FI
04.01.10
SQL> SELECT TRUNC(TO_DATE('0101&&year','MMDDYYYY'),'IW') FROM DUAL
  2  /
TRUNC(TO
28.12.09
SQL> 2 user10772980:
Use:
SELECT  TRUNC(TO_DATE('0101&&year','MMDDYYYY'),'IW') + (&&week-1)*7 FISCAL_YEAR_&&YEAR._WEEK_&&WEEK
  FROM  DUAL
FISCAL_YEAR_2010_WEEK_1
28.12.09
SQL> SY.