Re: BCNF and relational algebra
Date: Mon, 23 Feb 2004 01:56:31 +0000 (UTC)
Message-ID: <c1bmkf$6r$1_at_titan.btinternet.com>
"Bob Badour" <bbadour_at_golden.net> wrote in message
news:vr2dnf6SC-bv1aTd4p2dnA_at_golden.net...
> "Perception" <perceptionist2000_at_yahoo.com> wrote in message
> news:c1bcs9$89q$1_at_hercules.btinternet.com...
> > "Bob Badour" <bbadour_at_golden.net> wrote in message
> > news:NY2dnV0uDtJmkKTdRVn-uw_at_golden.net...
> > > What do you suppose the unary relation of dates means?
> > >
> > >
> >
> > Thanks for the reply.
> >
> > To answer your question: the unary relation means that every date is
> > associated with more than one value for every other attribute (that is,
> Date
> > only determines itself).
>
> That tells me what Date determines, but it does not tell me what it means.
> Is every date for all time in the unary relation? What does it mean for a
> specific date if it is in the relation? What does it mean for a specific
> date if it is not in the relation?
>
Sorry for the misunderstanding. Specific dates correspond to when a patient visited a doctor. Thus if a date is in the relation, it means a patient had seen a doctor/attended a clinic on that date.