How to get week starting with sunday date

Question

Hi
I have a date column "start_date", i need to create a report for all the weeks starting from sunday , for eg:
i need to get week dates as :
mm/dd/yy - 01/23/11 , 01/16/11 , 01/09/11 and so on...
Please help
Thanks...

Answer 1

Hi,
To find the last Sunday before or equal to start_date:
SELECT     TRUNC ( start_date + 1
           , 'IW'
           ) - 1          AS week_start_date
...You can use an expression like this in a GROUP BY clause, also.
This does not depend on you NLS settings. ISO weeks always start on Monday. Your week starts 1 day earlier, so that's why the expression above has the +1 and -1.
(Depending on you NLS settings,
SELECT     TRUNC ( start_date
           , 'D'
           )          AS week_start_date
...might do the same thing, but I still rocommend using 'IW'; a few extra keystrokes isn;t much to pay for a guarantee that it will always work.)
I hope this answers your question.
If not, post a little sample data (CREATE TABLE and INSERT statements) and the results you want from that data.