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Cc: Andrew Sullivan <ajs@crankycanuck.ca>,
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From: Kristo Kaiv <kristo.kaiv@skype.net>
Subject: Re: current_date / datetime stuff
Date: Tue, 5 Jun 2007 00:08:28 +0300
To: Michael Glaesemann <grzm@seespotcode.net>

oneliner:

select date_trunc('month',now()) + ((8 - extract('dow' from date_trunc 
('month',now()))||'days')::text)::interval;

Kristo
On 04.06.2007, at 19:39, Michael Glaesemann wrote:

>
> On Jun 4, 2007, at 10:59 , Michael Glaesemann wrote:
>
>>
>> On Jun 4, 2007, at 10:27 , Andrew Sullivan wrote:
>>
>>> On Mon, Jun 04, 2007 at 10:04:37AM -0500, Joshua wrote:
>>>> that will return the date of the first Monday of the month?
>>>
>>> I guess you need to write a function to do this.  I suppose you  
>>> could
>>> do it by finding out what day of the week it is and what the date  
>>> is,
>>> then counting backwards to the earliest possible Monday.
>>
>> As Andrew said, there's no built-in function to do this, but it's  
>> easy enough to write one. Here's a rough example (very lightly  
>> tested and probably overly complicated)
>
> And a little simpler:
>
> CREATE OR REPLACE FUNCTION first_dow_of_month(DATE, INTEGER)
> RETURNS DATE
> IMMUTABLE
> LANGUAGE SQL AS $_$
> SELECT v_first_day_of_month + ( 7 + $2 - v_day_of_week) % 7
>        AS first_dow_of_month
> FROM (
>      SELECT v_first_day_of_month
>             , extract('dow' from v_first_day_of_month)::integer
>                             AS v_day_of_week
>      FROM (SELECT date_trunc('month', $1)::date)
>           AS mon(v_first_day_of_month)) as calc;
> $_$;
>
> CREATE OR REPLACE FUNCTION first_monday(DATE)
> RETURNS DATE
> IMMUTABLE
> LANGUAGE SQL AS $_$
> SELECT first_dow_of_month($1, 1);
> $_$;
>
> Michael Glaesemann
> grzm seespotcode net
>
>
>
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