Re: A neutral challenge.

"Lauri Pietarinen" <lauri.pietarinen_at_atbusiness.com> wrote in message news:3EFA84EB.4000903_at_atbusiness.com...
> Bob Badour wrote:
>
> >When I attended Chris Date's UCLA Extensions course last year, it occured
to
> >me that subtypes and type generators go a long way to expressing many
> >recurring events as intervals. If THIRD_THURSDAY is a subtype of THURSDAY
is
> >a subtype of DAY, one might express an event on the third thursday of
every
> >month using an interval type INTERVAL_THIRD_THURSDAY.
> >
> >The gaps one must cross are that INTERVAL_THIRD_THURSDAY is neither a
> >subtype of INTERVAL_THURSDAY nor of INTERVAL_DAY and that the calendar
> >probably schedules events at a finer granularity than days. One would
need a
> >way of recasting interval types so that the third thursdays in one type
of
> >interval become days in a different type of interval, and then combine
those
> >days with a time of day to construct finer granularity schedules.
> >
> >Obviously declaring types for THIRD_THURSAY and SECOND_WEDNESDAY etc.
would
> >be tedious, so I think type generators for various date and time
> >granularities probably make sense too.
> >
> I think using types for this purpose is a slight overkill. It would be
> easy to add a 'day of week' and
> a 'day of week in month' column into materialised calendar and just use
> them in selection criterias.

This would complicate queries too much. If one wants to see the events on thursday, one would have to query three or more columns instead of querying a single interval column. Received on Fri Jun 27 2003 - 01:12:23 CEST