Re: Intersection of two date interval

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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