Re: Idempotence and "Replication Insensitivity" are equivalent ?

From: vc <boston103_at_hotmail.com>
Date: 22 Sep 2006 18:50:26 -0700
Message-ID: <1158976226.346905.308290_at_m7g2000cwm.googlegroups.com>


Aloha Kakuikanu wrote:
> vc wrote:
> > According to ANSI SQL, nulls are ignored in the aggregate functions
> > (except count(*)). It may not make sense to you, but it makes sense
> > to a lot of other folks.
>
> Or yeah, those folks defined null as a neutral element for sum
> aggregate too. Apparently they are unaware of identity:
>
> 0 + 0 + ... = 0

The above does not make any obvious sense. What's a "neutral element" ?

>
> > > It is obvious that you are after neutral elements -oo and +oo such that
> > >
> > > MIN(d, -oo) = -oo
> > > MAX(d, -oo) = d
> > > MIN(d, +oo) = d
> > > MAX(d, +oo) = +oo
> >
> > What's +oo in, say, the set of integers ?
>
[...]

> What I'm saying is that you have to define different neutral elements
> for different aggregates in order to maintain elementary consistency

Could you, like, you know, rephrase that ?

> A little imagination on the interpretation of +infinity and -infinity
> elements in the domain of computer number representations may help.

So what do imagine +oo is "in the domain of computer number representations " ? What specific representation and of what do you have in mind ? Received on Sat Sep 23 2006 - 03:50:26 CEST

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