Re: Lucid statement of the MV vs RM position?

From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Sat, 06 May 2006 13:42:29 +0200
Message-ID: <e3i233$7h4$1@orkan.itea.ntnu.no>

Marshall Spight wrote:
> Marshall Spight wrote:

>> Isn't GROUP an aggregate operator?

>
> To expand:
>
> GROUP : UNION :: SUM : +
>
> GROUP is to UNION as SUM is to PLUS.

I don't agree completely. UNION is a set operator; the individual values that you group in a GROUP operation aren't sets. But since I don't fully accept GROUP being an aggregate operator, I won't/can't explore this further.

> Interestingly, UNION is parametrically polymorphic, which
> raises the issue of parametrically polymorphic aggregate
> operators.

Isn't SUM also? It works on both integers and rationals; perhaps even dates.

BTW, TTM defines UNION and INTERSECT aggregate operators. They work on relations (RVAs).

-- 
Jon

Received on Sat May 06 2006 - 06:42:29 CDT