Re: Subtracting Two Intervals

Terry Lee Tucker wrote:
> In porting from 7.4.19 to 8.3.1 I have found the following:
>
> 7.4.19:
> mwr=# select interval '1 day 15 hours 30 minutes' - interval '29 hours';
> ?column?
> --------------------
> @ 10 hours 30 mins
> (1 row)
>
> 8.3.1:
> mwr83=# select interval '1 day 15 hours 30 minutes' - interval '29 hours';
> ?column?
> ----------------------------
> @ 1 day -13 hours -30 mins
> (1 row)
>
> Is that right? I mean if you take 1 day (24 hours) and add -13 hours and -30
> minutes, you get 10 hours and 30 minutes, but is it supposed to display that
> way?

We removed assumptions that every day is 24 hours between those
releases. You can use justify_hours() to get the proper result:

test=> select justify_hours(interval '1 day 15 hours 30 minutes' -
interval '29 hours');
justify_hours
---------------
10:30:00
(1 row)

There have been good arguments that justify_hours() behavior should be
the default.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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