Обсуждение: Last day of month

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> How to find the last sunday/mon..../sat of any given month.
There is probably a smoother way to do it, but here is a
quick little function to do what you ask. Feed it a date
and a number, where 0 is Sunday, 1 is Monday, etc.
CREATE OR REPLACE FUNCTION lastday(date,int) RETURNS DATE AS '
DECLARE match date; tomorrow date;
BEGIN
SELECT TO_DATE((SELECT EXTRACT(\'year\' FROM $1) || \' \' ||        EXTRACT(\'month\' FROM $1) || \' 01\'), \'YYYY MM
DD\')INTO tomorrow;
 
LOOP tomorrow := tomorrow + \'24 hours\'::interval; IF (1 = EXTRACT(\'day\' FROM tomorrow) ) THEN   RETURN match; END
IF;IF ($2 = EXTRACT(\'dow\' FROM tomorrow)) THEN   match := tomorrow; END IF;
 
END LOOP;
END;
' LANGUAGE plpgsql;
- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200402252206
                                   
 
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Greg Sabino Mullane wrote:
>>How to find the last sunday/mon..../sat of any given month.
>  
> There is probably a smoother way to do it, but here is a
> quick little function to do what you ask. Feed it a date
> and a number, where 0 is Sunday, 1 is Monday, etc.

How about this:

regression=# select date_trunc('month', current_date + '1 month'::interval);     date_trunc
--------------------- 2004-03-01 00:00:00
(1 row)

Joe

Greg Sabino Mullane wrote:
>>How to find the last sunday/mon..../sat of any given month.
>  
> There is probably a smoother way to do it, but here is a
> quick little function to do what you ask. Feed it a date
> and a number, where 0 is Sunday, 1 is Monday, etc.

oops...forget my last reply...I was a bit too quick on the draw. Try 
this instead:

regression=# select date_trunc('month', current_date + '1 
month'::interval) - '1 day'::interval;      ?column?
--------------------- 2004-02-29 00:00:00
(1 row)

Joe

At 11:30 PM 2/25/04, Joe Conway wrote:

>Greg Sabino Mullane wrote:
>>>How to find the last sunday/mon..../sat of any given month.
>>
>>There is probably a smoother way to do it, but here is a
>>quick little function to do what you ask. Feed it a date
>>and a number, where 0 is Sunday, 1 is Monday, etc.
>
>oops...forget my last reply...I was a bit too quick on the draw. Try this 
>instead:
>
>regression=# select date_trunc('month', current_date + '1 
>month'::interval) - '1 day'::interval;
>       ?column?
>---------------------
>  2004-02-29 00:00:00
>(1 row)
>
>Joe


But the original request was for a specific day-of-week.  So use Joe's 
answer above to get last day of month, and use 'dow' to determine the 
day-of-week of that day.  Let's call that dow1.  If the day-of-week being 
asked for is dow2 then:        if dow1 < dow2                return (last-day-of-month - dow1 - 7 + dow2)        else
            return (last-day-of-month - dow1 + dow2)
 
I'm no good at coding pgsql functions, so I'm not going to attempt proper 
syntax.

Frank 

On Thu, Feb 26, 2004 at 03:07:52AM -0000, Greg Sabino Mullane wrote:
> 
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> Hash: SHA1
>  
>  
> > How to find the last sunday/mon..../sat of any given month.
>  
> There is probably a smoother way to do it, but here is a
> quick little function to do what you ask. Feed it a date
> and a number, where 0 is Sunday, 1 is Monday, etc.

select date_trunc('month', current_date + '1 month'::interval) - '1 day'::interval +       (((3 - 7 -
to_char(date_trunc('month',current_date + '1 month'::interval) -       '1 day'::interval,'D')::int) %7)||'
days')::interval;

The "3" is the day of week (1 = Sunday, 7 = Saturday).  This equation
will return the date of the last "x" of the current month.  Change
"current_date" to be whatever date you wish to find the last "x" of.

Michael
--
Michael Darrin Chaney
mdchaney@michaelchaney.com
http://www.michaelchaney.com/