Oracle-L: Re: Week - Date function!

From: Vladimir Begun <vladimir.begun_at_oracle.com>
Date: Fri, 28 Mar 2003 22:08:35 -0800
Message-ID: <F001.00575B59.20030328220835@fatcity.com>

Hello!

Sesi Odury wrote:
> Given a week between (1 - 52) for a particular year can we get all the
> dates within that week. Is there a function to do this in SQL???

Using the simple statement below you can get the first date of the week (according to ISO standard). Then you can either add 6 to get the last day of the week and use ranges for your task or using any 'pivot'-approach (you need 7 rows) you can get all 7 days/dates of the week.

DEFINE yr=1998
DEFINE wk=5

SELECT TRUNC(TO_DATE('2711&yr', 'DDMMYYYY'), 'IYYY') + (&wk - 1) * 7     AS date_from
      , TRUNC(TO_DATE('2711&yr', 'DDMMYYYY'), 'IYYY') + (&wk - 1) * 7 + 6 AS date_to

FROM sys.dual
/

Ranges can be used in case one does not have a possibility to use FBI, for example.

The statement below is a bit more complicated. This one does a simple check and returns nothing in case week number is out of range.

DEFINE yr=1998
DEFINE wk=53

SELECT TRUNC(TO_DATE('2711&yr', 'DDMMYYYY'), 'IYYY') + (&wk - 1) * 7     AS date_from
      , TRUNC(TO_DATE('2711&yr', 'DDMMYYYY'), 'IYYY') + (&wk - 1) * 7 + 6 AS date_to

FROM sys.dual
WHERE TO_NUMBER(

          TO_CHAR(
            TO_DATE('3112&yr', 'DDMMYYYY')
          + DECODE(TO_CHAR(TO_DATE('3112&yr', 'DDMMYYYY'), 'IW')
                  , '01', -7
                        ,  0
            )
          , 'IW'
          )
        ) >= &wk

AND &wk > 0
/

HTH[, if I did not make a mistake].

-- 
Vladimir Begun
The statements and opinions expressed here are my own and
do not necessarily represent those of Oracle Corporation.




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Author: Vladimir Begun
  INET: vladimir.begun_at_oracle.com

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Received on Sat Mar 29 2003 - 00:08:35 CST