Re: Codd provided appropriate mathematics ... (was Re: Relational and MV (response to "foundations of relational theory"))

On Thu, 26 Feb 2004 13:31:31 -0600, "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote:

>
>"Eric Kaun" <ekaun_at_yahoo.com> wrote in message
>news:k6r%b.50112$LX2.42031_at_newssvr33.news.prodigy.com...
>> As an aside in this discussion, I've seen "multivalued" defined 2
>different
>> ways in explanations of relational (some of which are really bad).
>>
>> 1. Where attribute A can hold a list of values (type LIST)
>> 2. Where there are attributes A1, A2, A3, A4 (for example), all of the
>same
>> type and meaning. For example, ADDR1, ADDR2, etc.
>>
>> Does 1NF refer to both of these? If not, what's the proper terminology for
>> each of these cases?
>
>Good question because it is likely clear to most data folks that 1, which is
>the one more often referred to as multivalued (there is a MultiValue
>trademark associated with one such model) and is not permitted by the
>relational model, is a much better strategy than 2, which is permitted.

The Relational Model permits relation typed attributes, so "multivalued" does not have any advantage. Collection typed attributes don't violate 1NF.

Relations are in 1NF by definition. With a RDBMS you can not violate 1NF even if you want.

Regards

   Alfredo Received on Fri Feb 27 2004 - 12:07:56 CET