Re: Interval Question

Check this out:
rnd=# show DateStyle;
DateStyle
-----------
SQL, MDY
(1 row)

rnd=# select interval '@ 3 days 4 hours 17 mins'::interval - '@ 3 days 6 hours
17 mins'::interval;
?column?
-----------
@ 2 hours
(1 row)

And...
rnd=# set DateStyle to postgres;
SET
rnd=# select interval '@ 3 days 4 hours 17 mins'::interval - '@ 3 days 6 hours
17 mins'::interval;
?column?
---------------
@ 2 hours ago
(1 row)

Here is my Version:
PostgreSQL 7.4.6 on i686-redhat-linux-gnu, compiled by GCC gcc (GCC) 3.2.3
20030502 (Red Hat Linux 3.2.3-42)

On Tuesday 11 January 2005 10:19 am, Tom Lane saith:
> Terry Lee Tucker <terry(at)esc1(dot)com> writes:
> > I thought that subtracting the larger interval from
> > the small would return this but it is always the absolute value.
>
> Eh?
>
> regression=# set DateStyle TO ISO;
> SET
> regression=# select '@ 3 days 4 hours 17 mins'::interval -
> regression-# '@ 3 days 6 hours 17 mins'::interval;
> ?column?
> -----------
> -02:00:00
> (1 row)
>
> regression=# set DateStyle TO postgres;
> SET
> regression=# select '@ 3 days 4 hours 17 mins'::interval -
> regression-# '@ 3 days 6 hours 17 mins'::interval;
> ?column?
> ---------------
> @ 2 hours ago
> (1 row)
>
> and as for detecting whether it's negative,
>
> regression=# select ('@ 3 days 4 hours 17 mins'::interval -
> regression(# '@ 3 days 6 hours 17 mins'::interval) < '0'::interval;
> ?column?
> ----------
> t
> (1 row)
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
> joining column's datatypes do not match

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