Re: Key attributes with list values was Re: What are the differences ...KEY
Date: Mon, 27 Feb 2006 15:56:29 GMT
By revealing an attribute that reflects the identity of a proposition with respect to all other propositions in the database. For lack of a better term, I'll call it an identity attribute. I dislike the term "surrogate" because that implies the existence of an entity, and there is a subtle difference between a surrogate and an identity attribute. A surrogate value indicates that a distinct entity exists; an identity attribute value indicates that a proposition became known by the database. Regardless of the semantics, revealing or adding an additional immutable key is the only mechanism that allows a constraint that involves more than one database state to be enforced by the database.
"Anith Sen" <anith_at_bizdatasolutions.com> wrote in message
>>> I really didn't think I needed to state the obvious. The key is the
>>> name of a person. For the purpose of this discussion it doesn't matter
>>> whether it's modeled as a single attribute or two. Only the person's
>>> name and marital status belong to the universe of discourse.
> With those propositions, how do you make sure that the DBMS is aware of
> the fact that Jane Harper and Jane Smith are the same entity?
Received on Mon Feb 27 2006 - 16:56:29 CET