Re: Constraints and Functional Dependencies
From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 24 Feb 2007 16:21:59 GMT
Message-ID: <HCZDh.1129723$R63.5407_at_pd7urf1no>
Date: Sat, 24 Feb 2007 16:21:59 GMT
Message-ID: <HCZDh.1129723$R63.5407_at_pd7urf1no>
Marshall wrote:
> On Feb 24, 6:41 am, paul c <toledobythe..._at_oohay.ac> wrote:
> ...
> Yeah. You'd need another constraint to express that, and I don't think
> it would be possible to express the constraint that foreign keys must
> reference primary keys, because that would be a second order
> formula: it quantifies over formulas.
> ...
If that's true, doesn't it mean that requiring the referenced attribute to be key can't be a consequence of the strict RM which assumes FOL?
p Received on Sat Feb 24 2007 - 17:21:59 CET