Re: Video rental shop

"mgkiourt" <mgkiourt_at_otenet.gr> wrote in message news:<9k40k2$2bn2$1_at_ulysses.noc.ntua.gr>...
> The video rental shop classifies movie titles according to their type:
> classical,western,new release.
> Each type cotains many possibble titles and most titles within a type are
> available in multiple copies.
> Movies classified as new releases are reclassified to an appropriate type
> after they have been in stock for thirty days.
> Any help?
> Thanks.Mike

Okay, logical relationships:

shop ->> titles

title -> genre

genre ->> title

copy -> title

title ->> copy

copy -> title

Approach new titles in one of two ways. Either make new titles a genre with an action that raises a flag for hand re-classification in thirty days, or make a separate new title relation that only keeps titles for thirty days.

Making new title a genre may reduce the amount of machinery you have to build, and waiting 30 days to assign the regular genre would give you time to get opinions on the assignment of genre (as in a flick that looks like a western but turns out to be an American gothic romance).

The new title relation would look like

title -> age

age ->> title

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.

You might also have two genre, a publisher's classification and a customer's classification:

title -> pub_genre

pub_genre ->> title

title -> cust_genre

cust_genre ->> title

And new title be a possible value for cust_genre, with an action to set a flag for manual re-classification at thirty days.

Shoot, if you really wanted to, you could have arbitrarily many genre, but why bother?

And if I've just done your homework assignment, don't blame me if it's not what your teacher wanted. You'll probably need to fill it out a bit and check it before you use it, at minimum.

Joel Received on Fri Aug 03 2001 - 12:47:58 CEST