Getting the week number for a given date

Question

Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production
PL/SQL Release 11.1.0.7.0 - Production
CORE     11.1.0.7.0     Production
TNS for 64-bit Windows: Version 11.1.0.7.0 - Production
NLSRTL Version 11.1.0.7.0 - Production
Hello all.
I am currently migrating our product from SQL SERVER to ORACLE and have the following issue.
Basically I'm just trying to get the year week number for a given date but I'm having trouble with Oracle as it seems to think that the weeks run from Thursday to Thursday?. I presume this is something to do with the fact that the first day of the year was Thursday?
e.g.
SQL SERVER:
select DATEPART(wk, '2009-10-24') as Sat -- 43 - correct
select DATEPART(wk, '2009-10-25') as Sun -- 44 - correct
select DATEPART(wk, '2009-10-26') as Mon -- 44 - correct
select DATEPART(wk, '2009-10-27') as Tue -- 44 - correct
select DATEPART(wk, '2009-10-28') as Wed -- 44 - correct
select DATEPART(wk, '2009-10-29') as Thu -- 44 - correct
select DATEPART(wk, '2009-10-30') as Fri -- 44 - correct
select DATEPART(wk, '2009-10-31') as Sat -- 44 - correct
select DATEPART(wk, '2009-11-1') as Sun -- 45 - correct
select DATEPART(wk, '2009-11-2') as Mon -- 45 - correct
select DATEPART(wk, '2009-11-3') as Tue -- 45 - correct
select DATEPART(wk, '2009-11-4') as Wed -- 45 - correct
select DATEPART(wk, '2009-11-5') as Thu -- 45 - correct
ORACLE:
SELECT to_char(to_date('24-OCT-2009'), 'ww') as Sat from dual; -- 43 correct
SELECT to_char(to_date('25-OCT-2009'), 'ww') as Sun from dual; -- 43 incorrect - should be 44
SELECT to_char(to_date('26-OCT-2009'), 'ww') as Mon from dual; -- 43 incorrect - should be 44
SELECT to_char(to_date('27-OCT-2009'), 'ww') as Tue from dual; -- 43 incorrect - should be 44
SELECT to_char(to_date('28-OCT-2009'), 'ww') as Wed from dual; -- 43 incorrect - should be 44
SELECT to_char(to_date('29-OCT-2009'), 'ww') as Thu from dual; -- 44 correct
SELECT to_char(to_date('30-OCT-2009'), 'ww') as Fri from dual; -- 44 correct
SELECT to_char(to_date('31-OCT-2009'), 'ww') as Sat from dual; -- 44 correct
SELECT to_char(to_date('1-NOV-2009'), 'ww') as Sun from dual; -- 44 incorrect - should be 45
SELECT to_char(to_date('2-NOV-2009'), 'ww') as Mon from dual; -- 44 incorrect - should be 45
SELECT to_char(to_date('3-NOV-2009'), 'ww') as Tue from dual; -- 44 incorrect - should be 45
SELECT to_char(to_date('4-NOV-2009'), 'ww') as Wed from dual; -- 44 incorrect - should be 45
SELECT to_char(to_date('5-NOV-2009'), 'ww') as Thu from dual; -- 45 correct
Now I don't want to get into a discussion with regard to locales etc.
In my world (and is seems SQL SERVER's) the first day of the week is Sunday and the last Saturday.
Is there some NLS_? setting or something that I'm missing?
thanks for any help on this.
Andy

Answer 1

This is what you need.
SELECT ceil(( 7+(trunc(to_date('25-OCT-2009'),'d')-trunc(to_date('25-OCT-2009'),'Y')) )/7) FROM dual
HTH!!!
--tested all these statements.
Works as you wish!!
SELECT ceil(( 7+(trunc(to_date('24-OCT-2009'),'d')-trunc(to_date('24-OCT-2009'),'Y')) )/7) as Sat from dual;
SELECT ceil(( 7+(trunc(to_date('25-OCT-2009'),'d')-trunc(to_date('25-OCT-2009'),'Y')) )/7) as Sun from dual;
SELECT ceil(( 7+(trunc(to_date('26-OCT-2009'),'d')-trunc(to_date('26-OCT-2009'),'Y')) )/7) as Mon from dual;
SELECT ceil(( 7+(trunc(to_date('27-OCT-2009'),'d')-trunc(to_date('27-OCT-2009'),'Y')) )/7) as Tue from dual;
SELECT ceil(( 7+(trunc(to_date('28-OCT-2009'),'d')-trunc(to_date('28-OCT-2009'),'Y')) )/7) as Wed from dual;
SELECT ceil(( 7+(trunc(to_date('29-OCT-2009'),'d')-trunc(to_date('29-OCT-2009'),'Y')) )/7) as Thu from dual;
SELECT ceil(( 7+(trunc(to_date('30-OCT-2009'),'d')-trunc(to_date('30-OCT-2009'),'Y')) )/7) as Fri from dual;
SELECT ceil(( 7+(trunc(to_date('01-NOV-2009'),'d')-trunc(to_date('01-NOV-2009'),'Y')) )/7) as Sat from dual;
SELECT ceil(( 7+(trunc(to_date('02-NOV-2009'),'d')-trunc(to_date('02-NOV-2009'),'Y')) )/7) as Sun from dual;
SELECT ceil(( 7+(trunc(to_date('03-NOV-2009'),'d')-trunc(to_date('03-NOV-2009'),'Y')) )/7) as Mon from dual;
SELECT ceil(( 7+(trunc(to_date('04-NOV-2009'),'d')-trunc(to_date('04-NOV-2009'),'Y')) )/7) as Tue from dual;
SELECT ceil(( 7+(trunc(to_date('05-NOV-2009'),'d')-trunc(to_date('05-NOV-2009'),'Y')) )/7) as Wed from dual;
SELECT ceil(( 7+(trunc(to_date('06-NOV-2009'),'d')-trunc(to_date('06-NOV-2009'),'Y')) )/7) as Thu from dual;
Cheers!!!
Bhushan
Edited by: Buga on Oct 29, 2009 10:46 AM