Re: compound propositions

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 29 Mar 2010 23:59:48 -0300
Message-ID: <4bb16925$0$12421$9a566e8b_at_news.aliant.net>



Mr. Scott wrote:
> "paul c" <toledobythesea_at_oohay.ac> wrote in message 
> news:2oprn.364$Z6.28_at_edtnps82...
> 

>>Mr. Scott wrote:
>>
>>>"paul c" <toledobythesea_at_oohay.ac> wrote in message
>>>news:XEvnn.71100$PH1.31420_at_edtnps82...
>>
>>...
>>
>>>>One reason is that I still don't know how Codd's Information Principle
>>>>applies to compound propositions, eg., " 'C1' is a customer OR 'C1' is a
>>>>client". I can see that humans might imagine themselves capable of
>>>>interpreting a relation (or to put it redundantly a relation value) as
>>>>implitly mentioning that 'OR' connective (and dba's might so instruct
>>>>their users). But where is it recorded? (or 'manifested'?) Eg., is it
>>>>'recorded' only in the ephemeral form of an expectation that a program's
>>>>execution can't manifest given a single relation to operate on?
>>>
>>>I'm confused. Are you trying to find a way to avoid using nulls? ...
>>
>>No, I didn't have that in mind. Until I can put the question more
>>coherently I do have a comment about 'avoiding nulls' and no offense
>>intended - the phrase seems so unfortunate to me, as if it means some kind
>>of detour or deviation from orthodoxy. Not unlike how so many expressions
>>in other fields sooner or later acquire the opposite meaning from the
>>original. I suppose 'avoiding nonsense' covers the same intended ground
>>but bothering to keep either figment constantly in mind seems a waste of
>>time to me. I suppose there are purists in all fields who feel a need to
>>rebut every cockamamie nuance spouted by half-assed practitioners.
> 
> Nulls are not nonsense.  They're merely a device that permits the recording 
> of disjunctive information in neat tabular format. 

Explain how that requires breaking useful identies like

SUM(A) + SUM(B) = SUM(A+B) create table tablewithnulls(A integer, B integer)

insert into tablewithnulls values(1,NULL)
insert into tablewithnulls values(NULL,2)
insert into tablewithnulls values(3,4)

select SUM(A) from tablewithnulls      -- 4
select SUM(B) from tablewithnulls      -- 6
select SUM(A+B) from tablewithnulls -- 7 != 4+6 Received on Mon Mar 29 2010 - 21:59:48 CDT

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