Date: Fri, 26 Jan 2007 10:50:08 +0100
From: "A. Kretschmer" <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: Intersection of two date interval
Message-ID: <20070126095007.GD15591@a-kretschmer.de>
References: <49a67b230701260139n1153ee82x8ae91875118f3cd2@mail.gmail.com>
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am  Fri, dem 26.01.2007, um 11:39:03 +0200 mailte Suha Onay folgendes:
> Hi,
> 
> How can i find the number of days in the intersection of 2 date interval?
> For example:
> 1st  interval: (10.01.2007, 20.01.2007)
> 2nd interval: (13.01.2007, 21.01.2007)
> The intersection dates are: 13,14,15,16,17,18,19, 20
> The result is: 8
> 
> How can i find the result, 8 in an sql query without using CASE statements?


Some time ago i wrote a function for this, i hope it's helpfull for you:
(not realy tested, be careful!)


create type start_end as (t1 timestamptz, t2 timestamptz);

create or replace function time_intersect (timestamptz, timestamptz, timestamptz, timestamptz) returns start_end as $$
declare
        _s1     alias for $1;
        _e1     alias for $2;
        _s2     alias for $3;
        _e2     alias for $4;
        _start  timestamptz;
        _end    timestamptz;
        _return start_end;
begin

        if _s1 < _s2 then
                _start := _s2;
        else
                _start := _s1;
        end if;

        if _e1 < _e2 then
                _end := _e1;
        else
                _end := _e2;
        end if;

        if _start < _end then
                _return.t1 := _start;
                _return.t2 := _end;
        else
                _return.t1 := NULL;
                _return.t2 := NULL;
        end if;

        return _return;
end
$$ language plpgsql;


test=# set datestyle=german;
SET
test=*# select time_intersect('10.01.2007'::date, '20.01.2007'::date, '13.01.2007'::date, '21.01.2007'::date);
                    time_intersect
-------------------------------------------------------
 ("13.01.2007 00:00:00 CET","20.01.2007 00:00:00 CET")
(1 row)


test=*# select *, t2-t1 from time_intersect('10.01.2007'::date, '20.01.2007'::date, '13.01.2007'::date, '21.01.2007'::date);
           t1            |           t2            | ?column?
-------------------------+-------------------------+----------
 13.01.2007 00:00:00 CET | 20.01.2007 00:00:00 CET | @ 7 days
(1 row)


Andreas
-- 
Andreas Kretschmer
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