Re: Clues on modeling a really simple concept

On 7 abr, 01:38, jefftyzzer <jefftyz..._at_sbcglobal.net> wrote:
> On Apr 6, 3:40 pm, Spike <fau..._at_gmail.com> wrote:
>
>
>
> > On 6 abr, 23:11, Bernard Peek <b..._at_shrdlu.com> wrote:
>
> > > In message
> > > <16d72645-6a6b-4fd4-bccf-d5002970f..._at_q2g2000vbr.googlegroups.com>,
> > > Spike <fau..._at_gmail.com> writes
>
> > > >My question is: Should i add a relationship between galleries and
> > > >users?
>
> > > >I would like to query which galleries a user has, and i don't really
> > > >know if it is worth adding a foreign key rather than doing a three-
> > > >level join query each time i want to obtain this data.
>
> > > Less is more. The database is fully normalised without adding an extra
> > > relationship. You shouldn't denormalise without a good reason.
> > > Denormalised systems are usually more fragile and will cost you more
> > > time in programming and maintenance.
>
> > > Of course if there is some other real-world relationship between
> > > galleries and users you may need to change the model. Do galleries have
> > > Owners, for instance and would those be Users?
>
> > > --
> > > Bernard Peek
>
> > Hi!
>
> > I was thinking about system performance vs. normalization. By adding
> > that extra relationship, three-level joins can be avoided, and so
> > stressing the dbms too much.
>
> > Do you think is a good idea in general to denormalize the data model
> > by means of performance?
>
> > Thanks!
>
> Spike,
>
> I'm not sure if you're deliberately trying to be provocative, but I'd
> say it's fair to characterize this newsgroup as denormalization-
> hostile ;-).
>

Its the very first time i post (and even read) this newsgroup, so no, im not deliberately provocative.

> What's more important, I think, is to put first things first, and as I
> hinted at--and others made explicit--what's paramount is getting the
> requirements right and accurately modeling the problem domain. If
> users create galleries, and/or galleries can exist independently of
> any pictures being assigned to them, then model accordingly. Period.
>
> Bottom-line, IMHO: 1) model the domain accurately, and 2) deviate from
> the model only when *truly* warranted (NB that often denormalization
> is zero-sum--who cares when the data comes back faster when it's wrong
> or contradictory?). You might want to see if you can find a copy of
> "The Normal Is So... Interesting" by Chris Date (DBP&D 11/97) for more
> on the topic of denormalization. Many other sources abound.
>

The problem here is that users should be able to upload pictures without specifying a particular gallery (i will use a default one). In a similar way, the should be able to create an empty gallery.

Thus, there are two options: make a relationship between users and galleries or create a record in the join table between pictures and galleries with null values on foreign keys.

I dont really like any of the two options, but if one of them increases overall performance, that will be a good decision maker.

> Regards,
>

Thanks!

> --Jeff
Received on Tue Apr 07 2009 - 02:16:26 CEST