Re: The horse race

"Daniel Dittmar" <daniel.dittmar_at_sap.corp> wrote in message news:dtf1lf$9hc$1_at_news.sap-ag.de...
> Mark Johnson wrote:
> > No that's a relation. In describing a race, the attributes might
> > include, gate. The gates are ordered.
> >
> > But as I understand it, relations are not supposed to be sorted. So I
> > wondered that if a relation includes a horse's ranking, as a 'thing'
> > intrinsic, that one is trying to say that relations can be sorted?
>
> In a database that is not set oriented, you could simply add horses to a
> race, the gate number would be implicit through the insertion order.
>

It's this implicit data that contributed to the confused state of affairs before databases became widely used. If you assign a sequence number to the record or tuple at the moment of insertion, and carry that around as data all well and good. But if you use the list itself as implicitly carrying that information payload here's what can happen:

Someone who is unaware of the information payload in the given order discovers that sorting the list in some other order will yield superior performance, so that person reorders the list. No harm done, right? Then someone else comes along who is aware of the list ordering principle, but not of the recent reordering, uses the data to determine the original entry order.

Wrong data, wrong answers.

If anything can go wrong, it will. The above is not a hypothetical scenario. It's happened thousands of times. Received on Tue Feb 21 2006 - 15:21:30 CET