Re: How can I get the first and last date of a week, based on the week number and the year

On Feb 27, 2008, at 2:32 AM, Bruno Baguette wrote:

> Hello !
>
> I have a week number (ISO 8601) and a year, based on theses values,
> I would like to get the first and the last dates of that week.
>
> How I can do that ?
>
> The only solution is doing a big generate_series to build a subset
> that contains the week of all the dates between the 01/01 || year
> and the 31/12 || year. But I find that solution quite dirty and
> ressources consumming.
>
> Is there a cleanest way to do that ?

You can use to_date for most of that, like:
development=> select to_date('01 02 2008', 'ID IW YYYY') AS start,
to_date('07 02 2008', 'ID IW YYYY') AS end;
start | end
------------+------------
2008-01-07 | 2008-01-07
(1 row)

I'm a bit surprised that specifying the weekdays doesn't make any
difference here, maybe it's my version?:

development=> select version();
version
------------------------------------------------------------------------
------------------------
PostgreSQL 8.2.4 on i386-portbld-freebsd6.2, compiled by GCC cc
(GCC) 3.4.6 [FreeBSD] 20060305
(1 row)

Anyway, you can solve that by adding an interval '6 days' to the end
result.

Alban Hertroys

--
If you can't see the forest for the trees,
cut the trees and you'll see there is no forest.

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