Re: O'Reilly interview with Date

Kenneth Downs wrote:
>
> Theoretically I think it is better that two columns of the same name must
> always have the same domain. It seems that those who would allow the
> opposite have the burden of proving the benefit.

I tend to agree, but there are issues. On the one hand, different tables
are different namespaces; on the other hand they aren't. I say they're the same because you might have to unify their column names when joining
(whether we standardize on natural join or not.) They are different because the constraint you propose is probably too onerous. If we have a database with thousands of attributes (which is quite possible) then we would probably be unhappy having attribute names required to be globally unique.

> Alas, this would break
> all of that sofware out there written by people who pay good money for db
> servers to Oracle, MS, IBM, and friends, so it is just not commercially
> viable at this time to introduce this restriction.

Since this is a theory newsgroup, I have the benefit of being able to wave my hands at that problem and pretend it isn't there. :-)

> BTW, why do you have two unique columns, do you allow people to change their
> logins? Otherwise I would think they are redundant.

Just as you surmise. People get married and change their names, for example, and are unhappy having to keep a login that's mostly or entirely a name they don't use anymore.

> But anyway, moving forward, a query is just a list of desired columns (we
> apply to user's filters like defect=123 at runtime) from tables, so the
> query would be:
>
> query Myquery {
> table bugs {
> column { bugid; }
> }
> foreign_key users {
> suffix: _rep;
> column { login; }
> }
> foreign_key users {
> suffix: _own;
> column { login; }
> }
> }

Okay. What are the three column names of the result set? is it (bugid, login_rep, login_own) ? If so, I would say that you do, in fact, address the namespace unification issue.

Marshall Received on Fri Aug 12 2005 - 09:17:17 CEST