Re: Interval Question

On Tue, 11 Jan 2005, Terry Lee Tucker wrote:

> As you can see, this truck is going to be 2 hours late. The return value I'm
> looking for is the difference between Appt. Interval and Travel Interval, as
> in: return (appt_interval - travel_interval). This value will be stored in a
> column of type interval. I would like for late values to be shown as
> negative. @ -2 hours. I thought that subtracting the larger interval from
> the small would return this but it is always the absolute value. The
> documentation states:
>
> interval values can be written with the following syntax:
>
> [(at)] quantity unit [quantity unit...] [direction]
>
> Where: quantity is a number (possibly signed);
>
> Considering the above statement I believed that I could show this difference
> as a negative value but I haven't been able to figure out how to do it. Can I
> do this, and if so, how?

Well, when I try this with constant values on my 7.4 or 8.0 dev system I
get:

select '3 days 4 hours 17 mins'::interval - '3 days 6 hours 17
mins'::interval;
?column?
-----------
-02:00:00
(1 row)

Can you give a full example?