Re: "Aggregate" operators
Date: Mon, 24 Apr 2017 20:59:52 +0200
Message-ID: <odlhv9$2fki$1_at_adenine.netfront.net>
On 24/04/2017 20:06, Erwin wrote:
> Looking for a *formal* definition of the term "aggregate" operator.
>
> The term is quite familiar and the one in common use to denote SQL
> operators such as MIN, MAX, AVG that occur exclusively in connection
> with some GROUP BY.
>
> However, "occur exclusively in connection with SQL GROUP BY" is rather
> non-mathematical as a formal definition and so, is anyone around here
> aware of something more rigorous as a *definition* of when some
> operator is or is not an "aggregate" operator ?
Off the top of my head, Klug's "Equivalence of Relational Algebra and Relational Calculus Query Languages Having Aggregate Functions" should have a formal definition.
And have you checked Alice's book?
Nicola Received on Mon Apr 24 2017 - 20:59:52 CEST