From: Brian Selzer <>
Date: Mon, 31 Dec 2007 04:01:45 -0500
Message-ID: <Zd2ej.2357$>

"Bob Badour" <> wrote in message news:47783be8$0$19877$
> JOG wrote:
>> On Dec 30, 10:46 pm, "Brian Selzer" <> wrote:
>>>"JOG" <> wrote in message
>>>>On Dec 30, 7:23 pm, "Brian Selzer" <> wrote:
>>>>>"stevedtrm" <> wrote in message
>>>>>>>>If everyone is clear NULLS shouldn't be used, why the debate as to
>>>>>>>>to do about them ?
>>>>>>>Because SQL allows NULL and even promotes the idea that NULL solves
>>>>>>>problem instead of introducing many.
>>>>>>So everyone is agreed that NULLs shouldn't appear anywhere, and its
>>>>>>just a matter of time before NULLS become a legacy problem and a
>>>>>>relational language supercedes SQL?
>>>>>No, Steve, not everyone is agreed.
>>>>>>Are the two solutions I suggested before the widely accepted as
>>>>>>resolutions to the two problems NULLs were introduced to eradicate?
>>>>>>>Missing information? Then surely there should just be no tuple?
>>>>>A row may contain a lot more information that would otherwise be
>>>>>Would you tell a potential customer that you won't serve them because
>>>>>don't know everything about them? I think not! Haven't you been asked
>>>>>your e-mail address at a retailer? What would you think if the cashier
>>>>>you to get lost for refusing to supply it?
>>>>>>>To indicate that there can be no value? Why not a seperate table with
>>>>>>>a boolean value in the non-key column?
>>>>>In my opinion, null should only ever be used to indicate "There should
>>>>>value here, but it hasn't been supplied." That there should be a value
>>>>>that there must be a value are structural issues, and therefore should
>>>>>be subject to interpretation. "No value here" invites interpretation,
>>>>>because it begs the question, "Should there have even been a value?"
>>>>>Structural information is lost by separating a nullable column into its
>>>>>table: the fact that there should always be a value, even if it hasn't
>>>>>supplied is lost.
>>>>I think this could be put better. It is not that there should always
>>>>be a value, but rather that "a value exists in the real world".
>>>>However I don't really see what is structurally lost by complete
>>>>decomposition to eliminate nulls, that can't be remedied via
>>>If you complete the interpretation such that all missing values are
>>>supplied, then the resulting database should be a set of relations. When
>>>there is a nullable column on a table, there will a 1:1 correspondence
>>>between values in the completed relation. The problem with separating a
>>>column that can contain nulls into another table is that when all missing
>>>values are supplied, there is no requirement that for every tuple in the
>>>referenced relation there must be one and only one tuple in the
>>>relation. Adding a constraint to guarantee that 1:1 correspondence would
>>>the same as not permitting the information to be missing in the first
>>>Thus the only ways that I can see to remedy that would be either to add a
>>>boolean column, or to add another table.
>> Could you clarify why you think using nulls maintain structural
>> information? If one is saying that a datum /must/ exist as part of the
>> proposition, why is there a nullable column allowing it not to?
>> Perhaps you are saying that the nullable column is stating that the
>> value "should be" part of the proposition, but "we're being a bit lax
>> about it" whereas a decomposed version does not?
>> If so, I am unclear at the moment what the value of this is - perhaps
>> you could refer me to an example of when it would be necessary?
> JOG,
> Selzer is an idiot. If the dbms guaranteed 1:1 correspondence, it would
> not be nullable in the first place. If decomposed, the relative
> cardinality is 1:{0 or 1} and not 1:1.
> The Information Principle makes explicit the idea that encoding any
> information in the structure is just plain, blind stupid. If one has a
> clue, one encodes all information in data values.

You're exhibiting your obtuseness again, Bob. Perhaps you should try thinking before posting. (That assumes, of course, that you have the ability to think, which in light of the content of your posts, your inability to be civil, and lately your misuse of the English language is in serious doubt.) Received on Mon Dec 31 2007 - 10:01:45 CET

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