Re: converting a specified year and week into a date

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On 02/14/07 02:13, A. Kretschmer wrote:
> am  Wed, dem 14.02.2007, um  2:01:09 -0600 mailte Ron Johnson folgendes:
>>>> i was just wondering if it was at all possible to turn a year and a given
>>>> week number into a real date just using postgresql commands?
>>>>
>>>>
>>>> e.g. if i have year = 2004 and week = 1,
>>>>     can i turn that into say 2004-01-01 (so that the specified
>>>>     date is the one for the beginning of week 1 in the year 2004
>>> You can extract the week from a given date with this:
>>>
>>> SELECT EXTRACT(WEEK FROM '2006-01-01'::date);
>>>
>>> Be careful, the 1.1. can be in the 52. week in the last year. If you
>>> know the first day in the year in week 1, then you can add 7* the given
>>> week-1 days to this date.
>> I think she wants to do the opposite: cast 2004w1 to YYYY-MM-DD format.
>
> I know, but to do this do you need to know the first day in this week...

But she does not know the first day of the week.

A lookup table would solve OP's question.  You'd have to populate
it, though.  Shouldn't be too hard.
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