Re: Thinking about MINUS

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sun, 07 Jan 2007 16:48:33 GMT
Message-ID: <Bv9oh.41744$cz.613288@ursa-nb00s0.nbnet.nb.ca>

paul c wrote:

> Walt wrote:
> ...
>

>> Either NOR or NAND are enough to bootstrap to the rest of it, provided 
>> you
>> make one little extension to them:
>>
>> NOR or NAND with only one operand is NOT.
>>
>> I don't know where it leads regarding database, either.  Just a random
>> thought.

>
> One of a couple of reasons this topic intrigues me is that certain
> scenarios aren't closed for operations in Codd's framework, eg., the
> case when two operands share an attribute name that has different types.
> I realize that a whole sub-industry has been built to deal with
> problems like this (based on various design disciplines, knowingly or
> unknowingly, I don't know), so many people would say I'm silly to
> wonder, but I can't help it.

Wouldn't one end up with a resulting attribute defined as a union-type in a relation with no rows? Received on Sun Jan 07 2007 - 10:48:33 CST