Re: Plural or singular table names

"Bob Badour" <bbadour_at_golden.net> wrote in message news:M9s5b.436$iP3.44134429_at_mantis.golden.net...
>
> > A relation value has no information about constraints.
>
> I disagree. Every relation has at least one candidate key, and the candidate
> keys can affect the result values of operations.

I notice you are not specifying relcon vs. relvar, which I conclude (from the fact that you're generally precise on these matters, and from context) that you mean both.

But I'm unable to figure out how what you're saying might apply to a relcon. Can you give me an example of an operation on one or two relational values and an associated operator that would be affected by the presence of a candidate key?

I guess I'm also assuming (much less solidly) that when you say candidate key, here, you are saying something *beyond* the fact that the rows must be unique. We would all agree (I hope!) that the members of a relation value are unique; I generally consider that part of the definition of relation, rather than that the definition includes the requirement of at least one candidate key, and that uniqueness is a consequence of that key.

Marshall Received on Thu Sep 04 2003 - 02:12:44 CEST