Обсуждение: Find Number Of Sundays Between Two Dates

Hai EverBody,

        Can I know what is the query by which we can find the number of
sundays between two given dates in postgres

Thanks In Advance,
Raghu.......
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am  Tue, dem 04.03.2008, um 22:16:07 -0800 mailte raghukumar folgendes:
>
> Hai EverBody,
>
>         Can I know what is the query by which we can find the number of
> sundays between two given dates in postgres

No problem, for instance for month january 2008:

test=*# select count(1) from
  (select '2008-01-01'::date + s*'1day'::interval as datum from
    generate_series(0,30) s)foo
  where extract(dow from datum)=6;
 count
-------
     4
(1 row)


With generate_series() i generate a list of dates, and later i check if
the date are a saturday. Okay, you need to know sunday -> change from 6
to 0 and ou course, you can calculate the parameter for the
generate_series like

test=*# select count(1) from
  (select '2008-01-01'::date + s*'1day'::interval as datum from
    generate_series(0,'2008-01-31'::date - '2008-01-01'::date) s)foo
  where extract(dow from datum)=0;
 count
-------
     4
(1 row)




Andreas
--
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net

On Wednesday 05 March 2008 06:16, raghukumar wrote:
> Hai EverBody,
>
>         Can I know what is the query by which we can find the number of
> sundays between two given dates in postgres
>
> Thanks In Advance,
> Raghu.......
I think the easiest way is to set up a table populated with all dates and days
between two years that are important to your application and then just do
simple selects on that table.
Regards
Garry

On 3/5/08, A. Kretschmer <andreas.kretschmer@schollglas.com> wrote:
>  With generate_series() i generate a list of dates, and later i check if
>  the date are a saturday. Okay, you need to know sunday -> change from 6
>  to 0 and ou course, you can calculate the parameter for the
>  generate_series like

I find it convenient to create a custom version of generate_series:

CREATE OR REPLACE FUNCTION generate_series(date,date)
  RETURNS SETOF date AS $$
    SELECT $1 + n FROM generate_series(0,$2-$1) AS x(n)
  $$ LANGUAGE SQL IMMUTABLE;

  Regards,
    Dawid