Re: Date's First Great Blunder

From: Leandro Guimarães Faria Corsetti Dutra <leandro_at_dutra.fastmail.fm>
Date: Fri, 23 Apr 2004 11:16:11 -0300
Message-ID: <pan.2004.04.23.14.16.11.366787@dutra.fastmail.fm>

Em Wed, 21 Apr 2004 14:37:23 -0700, Neo escreveu:

>> He does deal with missing information quite nicely, with the proposal to
>> include special values into each domain needing them. Looks like you
>> never understood the special values proposal.

>
> Special values are frequently masks for NULLs and still lead to 3VL. If
> john's age is "UNAVAILABLE" and mary's age is "UNAVAILABLE". Is john.age
> equal to or not equal to mary.age? (Unfortunately, understanding special
> values won't ever clear up this problem)

True, 3VL may me unavoidable, and it leads to more complexity.

Still, special values are not NULLs. NULLs are not values, and in SQL specifically they are dealt with incorrectly anyway.

-- 
Leandro GuimarÃ£es Faria Corsetti Dutra           +55 (11) 5685 2219
Av Sgto Geraldo Santana, 1100 6/71               +55 (11) 5686 9607
04.674-000  SÃ£o Paulo, SP                                    BRASIL
http://br.geocities.com./lgcdutra/

Received on Fri Apr 23 2004 - 09:16:11 CDT