Re: Proposal: 6NF
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 29 Sep 2006 23:09:25 GMT
Message-ID: <FIhTg.543$%6.18557_at_ursa-nb00s0.nbnet.nb.ca>
>
> How so? Plenty of people have nulls in 3NF. How is no nulls necessary
> for 1NF?
Date: Fri, 29 Sep 2006 23:09:25 GMT
Message-ID: <FIhTg.543$%6.18557_at_ursa-nb00s0.nbnet.nb.ca>
Karen Hill wrote:
>>Karen Hill wrote: >> >>>6NF would be a database that uses no Nulls. >> >>Um, "no nulls" is necessary for 1NF. And I >>believe someone already has dibs on "6NF."
>
> How so? Plenty of people have nulls in 3NF. How is no nulls necessary
> for 1NF?
There are basically two schools of thought on NULL. The SQL school and the consistent school. The consistent school observes that 1NF requires logical identity and what is sometimes called the Information Principle. These both require one represent all information explicitly as values, and NULL is not a value.
Hence, no table with a nullable column can be in 1NF let alone 3NF. The SQL school fudges the books ignoring both logical identity and the information principle.
Codd started down the SQL path with his RM V/2, but that path turned out to be the primrose path. Received on Sat Sep 30 2006 - 01:09:25 CEST