Re: Is it Possible to Enforce This Relationship at the DB Level?
Date: Mon, 22 Oct 2007 11:40:06 -0700
On 19 oct, 21:58, "David Portas"
> "dutone" <dut..._at_hotmail.com> wrote in message
> > On Oct 16, 4:03 am, David Portas
> > What I was trying to say is that not all constraints can be enforced
> > via relationships, hence the need for a RDMS to allow one to create a
> > high level constraint with statements like check assertion.
> I think you mean "not all constraints can be enforced by foreign keys
> alone". Am I right? I agree of course but you would be wrong to think that
> other types of constraint are not an equally legitimate part of conceptual
> and logical models. That's a mistake common to ER-modelling practice and
> it's a problem that ORM for example was specifically designed to correct.
> The problem being "I can't draw a picture of this relationship so it isn't
> part of my model!".
> You see why this is purely an implementation issue? A SQL CHECK or ASSERTION
> is not in principle at a "higher level" than a FOREIGN KEY constraint - it
> just looks that way because you don't like the syntax (actually, neither do
> David Portas
> > My original question appears to fall into this category, since I
> > cannot see away to guarantee that the Cell Config table will include
> > only rows of the Field table that are children of the Spec table
> > referenced by Spreadsheet Config.
> > Although maybe something was wrong with my model, which is why I
> > initially posted my question.
> > Thanks
I believe you will soon find out that dutone is a VI. Stop encouraging him into pouring more crap than he already poured down... Received on Mon Oct 22 2007 - 20:40:06 CEST