Re: "two time periods with only an endpoint in common do not overlap" ???

Think of it this way. When someone says they have a meeting from 1-2 and
another from 2-3, do those meetings overlap? They do not, because we're
actually saying the first meeting is from 1:00 through 1:59:59.99999. The
Postgres date ranges are the same way. The starting point is inclusive,
but the ending time is exclusive. So [1:00,2:00), and [2:00,3:00), do not
overlap.

On Fri, Oct 15, 2021 at 2:16 PM Ron <ronljohnsonjr(at)gmail(dot)com> wrote:

> On 10/15/21 8:59 AM, Adrian Klaver wrote:
> > On 10/15/21 06:52, Ron wrote:
> >> On 10/14/21 7:02 PM, Adrian Klaver wrote:
> >> [snip]
> >>> or the third example in the docs:
> >>>
> >>> SELECT (DATE '2001-02-16', DATE '2001-12-21') OVERLAPS
> >>> (DATE '2001-10-30', DATE '2002-10-30');
> >>> Result: true
> >>> SELECT (DATE '2001-02-16', INTERVAL '100 days') OVERLAPS
> >>> (DATE '2001-10-30', DATE '2002-10-30');
> >>> Result: false
> >>> SELECT (DATE '2001-10-29', DATE '2001-10-30') OVERLAPS
> >>> (DATE '2001-10-30', DATE '2001-10-31');
> >>> Result: false
> >>
> >> Why /don't/ they overlap, given that they share a common date?
> >
> > Per the docs:
> >
> > https://www.postgresql.org/docs/current/functions-datetime.html
> >
> > " Each time period is considered to represent the half-open interval
> start
> > <= time < end, unless start and end are equal in which case it
> represents
> > that single time instant."
> >
> > Which I read as
> >
> > (DATE '2001-10-29', DATE '2001-10-30') ends at '2001-10-29'
> >
> > and
> >
> > (DATE '2001-10-30', DATE '2001-10-31') starts at DATE '2001-10-30'
> >
> > so no overlap.
>
> I was afraid you were going to say that. It's completely bizarre, but
> seems
> to be a "thing" in computer science.
>
> --
> Angular momentum makes the world go 'round.
>
>
>