Re: BCNF and relational algebra

"Perception" <perceptionist2000_at_yahoo.com> wrote in message news: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.

How does a unary relation with only a date attribute say anything about a patient or a doctor or a clinic? Received on Mon Feb 23 2004 - 03:43:19 CET