# Re: Counting propositions

Date: Tue, 22 Jun 2004 22:51:12 +0300

Message-ID: <40d88cae$1_at_post.usenet.com>

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"Mikito Harakiri" <mikharakiri_at_iahu.com> wrote in message
news:h60Cc.24$da4.292_at_news.oracle.com...

*>
**> "x" <x-false_at_yahoo.com> wrote in message
*

news:40d884f8$1_at_post.usenet.com...

> > **** Post for FREE via your newsreader at post.usenet.com ****

*> > > Let's go through the list:
**> > >
**> > > AVG - nonfundamental, can be expressed in terms of SUM
**> > > STDDEV = SQRT(VARIANCE)
**> > > VARIANCE = (SUM(x*x)-(SUM(x)*SUM(x))/SUM(1))/(SUM(1)-1)
**> > >
**> > > Do you need mere examples to be convinced that there are only 4
**> > fundamental
**> > > aggregate operators?
**> > > 1. SUM = "+"*
**> > > 2. MIN = "/\"*
**> > > 3. MAX = "\/"*
**> > > 4. LIST = "||"*
**> >
**> > Nonsense.
**> > SUM([1])=1.
**> > COUNT([1,2,3,4])=4 !=SUM([1,2,3,4]).
**>
**> SUM(1) is abbreviation for "select SUM(1) from T"
**>
**> In other words "1" in SQL is a function that maps column value x into 1
*

for

> all x.

*>
**> In order to calculate "Count([1,2,3,4])"
**> (where I deliberately changed the case in order to avoid confusion with
***SQL
**

> syntax) we first apply function f:x->1 to each element of the bag.

*> Therefore,
*

> Count([1,2,3,4]) = Sum([f(1),f(2),f(3),f(4)])=Sum([1,1,1,1])

Yes. And for every such function "f" you get some more aggregate operators
...

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