Re: foreign key constraint versus referential integrity constraint

"Reinier Post" <rp_at_raampje.lan> wrote in message news:4aecc20f$0$14682$703f8584_at_news.kpn.nl...
> Mr. Scott wrote:
>
>>[...] Constraints specify what can and cannot be
>>assigned a positive truth value, they do not specify what has been
>>assigned
>>a positive truth value. Queries manipulate what has been assigned a
>>positive truth value or what can be derived from what has been assigned a
>>positive truth value.
>
> Formally: a database instance is a set of named relations,
> i.e. a mapping from names to relations.
> A database is a set of possible database instances, such that
> each instance maps the same names to relations with, per name, the same
> signature.
> It is defined by a database schema (which maps each relation name to its
> signature)
> and database constraints (which limit the possible combinations of
> relations
> to which the names are mapped). (I can go on and define 'signature',
> etc.)
> A database constraint is a predicate on database instances.
>
> A 'table' (in this context) is a named relation in a database instance,
> or perhaps a database restricted to that name (i.e. a relation name mapped
> to
> the set of all possible values for that relation).
>
> A 'view' (in this context) is a named mapping from database instances to
> relations.
>
> --
> Reinier

I really don't get what you're driving at. I also don't fully agree with your characterization. What's the point you're trying to make? Received on Sun Nov 01 2009 - 02:39:31 CET