Re: Demo: Modelling Cost of Travel Paths Between Towns

"Neo" <neo55592_at_hotmail.com> wrote in message news:4b45d3ad.0411141752.2459ac4c_at_posting.google.com...
> > > Yes, a separate table for states is the correct way to avoid redundant
> > > PA's (even if PA doesn't have any properties). Alan didn't provide
> > > such a schema thus he has redundant PA's.
> >
> > States do not need a seperate table because (at this point, anyway)
> > they have no properties.
>
> A separate table for states is need to avoid redundant PA's. Your
> current schema has redundant PAs. The first PA represent PA. The
> second PA also represents the same PA as the first. According to CJ
> Date, redundancy leads to update anomalies. Assuming no
> auto-sychronization, your db can be corrupted by modifying one of the
> PAs. Please reread chapter 10 and in particular pg 312 of "An Intro to
> Db Systems" 6th Ed.

YOU have absolutely NO IDEA what you are talking about. I have less and less respect for you as time goes on. PA is not redundant. If the exact same row (all attributes) were stored twice, there would be redundancy. According to your MIS-interpretation, PA would be stored once in, say, a STATES table, along with some state_id, say 31 for PA, and the number 31 would be stored multiple times in the data tables to represent PA. But then 31 is redundant by your bizzare thought process. Either that, or there can only be one row for all towns in PA. You make no sense. Does not speak well for Xdb. Received on Mon Nov 15 2004 - 15:46:08 CET