Re: Video rental shop

Bernard Peek <bap_at_shrdlu.com> wrote in message news:<rIlOTgCvArb7Ew45_at_diamond9.demon.co.uk>...
> In message <f0d5086.0108030247.28b2ae43_at_posting.google.com>, Joel Rees
> <jreesmf_at_mac.com> writes
>
>
>
> >
> >and the advantage here would be to be able to assign the genre when
> >the title is entered in the database, and have an action clear the new
> >title flag automatically.
>
> That's probably undesirable. The genre code isn't really a genre, it's
> likely to be a physical location code. New releases will be kept on a
> different shelf and moved to their genre shelf after 30 days. The action
> needed is to send a list of titles that need to be moved, and the shelf
> they should be moved to. It might be useful to have the staff confirm
> that they have physically moved the stock.
>
> This is an example of a code being overloaded with additional meanings.
> New Release is not really a genre, it's an extra code that might be
> stored in that field. Consider what happens in a really big video store
> where there might be a separate new release section within each genre.

Check out the Conceptual and Physical Data Models I created a while ago for a Video Rental Store on my Database Answers Web Site :-

   http://www.databaseanswers.com/data_models/video_rental_store/index.htm

Change the FACTs to reflect your requirementts, and then change the Model
accordingly :-

   http://www.databaseanswers.com/data_models/video_rental_store/facts.htm

It's probably easier to discuss the Physical Data Model, where I think you would
want to add a 'Genre', 'DateOfRelease' and/or 'DateArrivedInStore' to the MOVIE Entity :-
http://www.databaseanswers.com/data_models/video_rental_store/video_rental_physical.htm

The 'New release' is a derived attribute from ReleaseDate and therefore should not appear in the Data Model, although you might show it in the Database design for clarity or ease of programming or performance.

The design of the Physical Model shows a primary key which is a surrogate, and identifies each copy.

Hope this helps.

Barry Williams
Principal Consultant
Database Answers Received on Sun Aug 19 2001 - 13:57:36 CEST