Re: Question about Date & Darwen <OR> operator
From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 2 Sep 2005 17:11:31 -0700
Message-ID: <1125706291.163098.312610_at_g14g2000cwa.googlegroups.com>
Date: 2 Sep 2005 17:11:31 -0700
Message-ID: <1125706291.163098.312610_at_g14g2000cwa.googlegroups.com>
Mikito Harakiri wrote:
>
> >From http://c2.com/cgi/wiki?RelationalAlgebra
>
> a OR b : An extended form of union; if the headings of the operands
> differ, then "missing" attributes take on all possible values. Thus the
> result may be very large or even infinite. When the operands have the
> same heading, then this is the same as a traditional SQL UNION, except
> that all duplicates are always removed.
>
> This informal description matches the other alternative. What is the
> formal definition?
Is that sufficiently formal? What would constitute a sufficiently formal form?
Marshall Received on Sat Sep 03 2005 - 02:11:31 CEST