Re: Is relational theory irrelevant? (was Re: Dreaming About Redesigning SQL)

"Bob Badour" <bbadour_at_golden.net> wrote in message news:sZqdnURpMcikvzKi4p2dnA_at_golden.net...
> > > Express a quota query.
> >
> > select top 5 * from (
> > select * from emp order by sal
> > )
> >
> > What is the problem, besides "5*from" looking ugly?
>
> The ordered operand.

I'm sorry, but I'm totally at a loss as to why that's a problem. Any references for further info?

In fact, here's a larger question: it seems to me that neither SQL nor TTM make adequate provisions for the difference between well-ordered relations and partially-ordered relations. It seems to me the two cases have to be considered separately: the partially-ordered relation will be subject to the issues (specifically: ties) discussed in Practical Issues in Database Management (bing!: could that be what you're talking about, above?) but the well-ordered relation is not. And I think we'd want to preserve the distinction.

For example, we know if we sort using a total ordering function on a key column that we will have no ties.

Marshall Received on Tue Nov 11 2003 - 17:21:14 CET