Re: Is it Possible to Enforce This Relationship at the DB Level?
Date: Fri, 19 Oct 2007 17:09:20 -0000
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
> > 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
> 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.
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. Received on Fri Oct 19 2007 - 19:09:20 CEST