Re: abnormal forms

Bob Badour wrote:
> paul c wrote:
>

>> Bob Badour wrote:
>>
>>> ...
>>
>> If you have relation

Could be, once one is talking about an implementation. I didn't think I needed to go that far for a more elementary purpose.

> ...
>
> If you mean 'comparable' in the sense of the relational equality
> operator that compares two relations for equality, then the answer is
> yes. The result of the comparison is false.
>
>

>> and is it relationally comparable to
>>
>> 3. SP{S,P} with value
>>
>> S         P
>> =         -         (where the '=' underscore means S is a 'key')
>> 1         1
>> 2         1
>>
>> ?

I had in mind that there would be no such thing as an single valued-attribute except that all 'canonical' values would be single-element non-empty sets. I would have thought this could avoid typing errors.

 > ...

>> For sure, #3 is in a kind of canonical form as far as Codd was concerned.

Yes, I didn't want to make an example like that because to me it takes me toward negation and I haven't yet wrestled where that could lead. Same reason I tried to avoid talking about an 'equality operator'.

p Received on Thu Apr 20 2006 - 23:43:12 CEST