Re: looking for a term

mAsterdam wrote:
> paul c wrote:
> ...
> How would they differ in meaning?

perhaps i shouldn't have said 'meaning'. more straightforward to just say the ternary relation has a (implied) constraint that the two binary ones don't. actually several - eg if employee has a number, then employee must have a name and an address.

>

>> 2) if i natural join N and A, producing a result that matches the 
>> contents of E, am i introducing the constraint in some sense?

i guess if the constraint, implied or not, applies only to the view then inserts to A or N wouldn't be affected. if it were somehow enforced for A or N (for example, if A.emp# was a foreign key E.emp# and vice-versa, even if that seems a bizarre way to do it and similarly for N.emp#), then some 'transaction' mechanism would be needed for separate insert 'statements' to succeed, but that's another topic, i think.

perhaps the implied constraint i'm talking about is nothing more than a fancy way to say that nulls aren't allowed.

p Received on Sun Jul 10 2005 - 00:44:37 CEST