Re: Is it Possible to Enforce This Relationship at the DB Level?

On 19 oct, 19:09, dutone <dut..._at_hotmail.com> wrote:
> On Oct 16, 5:36 am, "David Cressey" <cresse..._at_verizon.net> wrote:
>
>
>
> > "David Portas" <REMOVE_BEFORE_REPLYING_dpor..._at_acm.org> wrote in message
>
> >news:1192532593.274612.315800_at_z24g2000prh.googlegroups.com...
>
> > > On 15 Oct, 22:59, dutone <dut..._at_hotmail.com> wrote:
>
> > > > I'd like to enforce this based on the data model and its
> > > > relationships.
> > > > Although to me, it doesn't seem possible without an additional layer
> > > > of logic.
> > > > The need for a check assertion in a RDMS tells me that cerain
> > > > cituations must be enforced at a higher level. This is one of them I
> > > > guess.
>
> > > Maybe your definition of a data model differs from mine. All such
> > > constraints are surely part of that model irrespective of what syntax
> > > the DBMS uses.
>
> > > If you have some particular DBMS in mind then maybe someone will have
> > > other suggestions about features supported by that product. Perhaps a
> > > redesign would also be possible but I'm reluctant to begin a design-by-
> > > newsgroup exercise.
>
> > Very good point. Design-by-newsgroup has almost always been based on flawed
> > analysis.
>
> > Second, "enforcing this based on the model" is clearly an implementation
> > issue, not a modeling issue.
>
> How so? What I am trying to do is pin down the entities/relationships
> involved in a process and, given the "model" that I've come up with,
> it appeared that certain relationships would lead to the model's
> integrity being violated. Although I was not sure, and thought maybe
> my model was flawed.
It's not the model which is flawed, it's your knowledge of data fundamentals which orevents you from making a distincton between the logical and physical layers. My head hurts with the amount of gibberish and crappola you pour down in a single sentence.

> Maybe you believe it's a implementation issue because the
> "enforcement" (in my case I was looking for enforcement via
> referential integrity) actually takes place at the logical level, but
> this does not mean that you have to forgo the concept when creating a
> conceptual diagram.
There would be no doubt to somebody who has read at least ONE book about RM that this is an implementation issue as both David Portas and David Cressey already pointed out. Buit you obviously lack the intellectual onnesty to recognize it. Received on Mon Oct 22 2007 - 20:38:00 CEST