Re: pro- foreign key propaganda?

"Brian Selzer" <brian_at_selzer-software.com> wrote in message news:PseYj.9097$nl7.5836_at_flpi146.ffdc.sbc.com...
>
> "David Cressey" <cressey73_at_verizon.net> wrote in message
> news:RkTXj.2139$Zy1.1952_at_trndny05...
> >
> > "jonniesavell" <jsavell_at_gmail.com> wrote in message
> >
news:9e62cc4a-4e40-4cf5-9503-2bd77e0ddf46_at_x19g2000prg.googlegroups.com...
> >>
> >> > I think you are confusing foreign keys with declarative referential
> >> > integrity. Foreign keys are a must and I'm sure your database uses
> >> > them.
> >> > What you are talking about (and I agree) is a constraint.
> >>
> >> OK. I am stupid. I thought that an instance of declarative referential
> >> integrity in DDL create a foreign key between one or two tables in the
> >> database.
> >>
> >
> > Not stupid. Just ignorant. The wonderful thing about ignorance is that
> > it
> > can be cured. Read up on the subject, as others have suggested.
> >
> > The above argument is about definitions.
> >
> >
> >> What's the difference?
> >
> > If I say "select * from orders inner join order_detail
> > on orders.order_no = order_detail.order_no;
> >
> > then order_details.order_no must be a "foreign key" regardless of
> > whether
> > it was declared as such in DDL.
> >
> > If in the above case, order_details.order_no is for some strange reason
> > NOT
> > a foreign_key reference to the corresponding row in orders, then you
are
> > the victim of a sadistic and perverse database designer. Or perhaps
just
> > a
> > supremely ignorant one.
> >
>
> I think you're mistaken, David.

Go back and read my comment again.

>A foreign key constraint is a database
> constraint that guarantees that whenever there is a row in a referencing
> table, there is one and only one row in the table it references.

I know that, and you should know by now that I know that.

A foreign key and a foreign key constraint are not the same thing.

[snippage] Received on Mon May 19 2008 - 14:39:21 CEST