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"x" <x-false_at_yahoo.com> wrote in message news:40d85df1$1_at_post.usenet.com...
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> "Mikito Harakiri" <mikharakiri_at_iahu.com> wrote in message
> news:DPYBc.18$da4.141_at_news.oracle.com...
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> > "Paul" <paul_at_test.com> wrote in message
> > news:CFWBc.19053$NK4.3265189_at_stones.force9.net...
> > > Isn't "select count(*)" a similar thing? You should explicitly name
the
> > > data columns you want. If you change the candidate keys it may change
> > > the whole interpretation of the propositions. In which case it may no
> > > longer be true that you want to count propositions.
> >
> > Count is unusual aggregate operator. Every other aggregate operator is
> > associated with a binary operation. Indeed, the SUM is iterative
> application
> > of "+", the MAX is iterative application of "max(x,y)" (or CASE ...).
> There
> > are few exceptions like AVG, but they can be viewed as redundant (or at
> > least less fundamental) operators.
>
> SUM(),MAX(),AVG() apply to a bag of values.
>
> > What operation COUNT is application of? The increment, of course. Unlike
> the
> > examples above, the increment is unary operation, so the COUNT shouldn't
> > really have an argument!
>
> COUNT() apply to a bag of values.
SUM(a,b,c,d) = ((a + b) + c) + d
where brackets are inessential, as "+" is associative operators. Therefore, I'm talking about expressing an operation with variable number of arguments in terms of binary operation. Received on Tue Jun 22 2004 - 11:39:32 CDT