Re: Proposal: 6NF

On Oct 5, 6:17 am, Sampo Syreeni <d..._at_iki.fi> wrote:
> On 2006-10-05, David Cressey wrote:
>
> > An outer join between two relational tables will, in general, produce
> > a table with nullable columns.
>
>I'd add that the same applies if we want the relational model to be
> closed under arbitrary unions.

The inner union operator does not require anything like nulls, obey closure, and furthermore has more desirable algebraic properties.

Marshall Received on Thu Oct 05 2006 - 19:01:36 CEST