Re: Demo: Modelling Cost of Travel Paths Between Towns

> > > > In RM's current solution, symbol and town name are the same thing
> > > > resulting in inflexiblity in above case. In XDb2's solutions a symbol
> > > > or string names a town which is a different thing than the symbol...
> > >
> > > What you are not realizing is that "town" would never be a Primary Key,
> > > so it is easy in the RM to have more than one town with the same name.
> >
> > True in general, but not when using the one-table schema provided by
> > Mr. Celko. Please show how the current RM solution can work if two
> > towns are named the same (ie change name of town c to a).
>
> town PK
> state PK
> main_postal_code PK
> start_date
> end_date

Thanks for demonstrating that Mr. Celko original schema does not handle two towns with the same name without schema changes.

> Philadelphia PA 19104 6/1/1682 11/12/2004
> Neodelphia PA 19104 11/12/2004 12/31/2999
>
> And, no - storing PA twice is not redundant.

Storing any thing (ie PA) twice is redundant. On way to prove redundancy is to change the second PA and see if data is corrupted (without triggers/code to synchronize them). Also, if a property is added to PA, will you add it the first PA, second PA, or both? I won't be agruing the above point any further in this thread (unless you bring out a new point) as it was already discussed at length in OT "A Normalization Question". Received on Sat Nov 13 2004 - 20:03:13 CET