Re: Proposal: 6NF

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. To me that seems somehow more elementary, and it also ties neatly with inheritance modelling: even if you represent entities of subtypes and supertypes by different relations, sometimes it's handier to work on their union.

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Sampo Syreeni, aka decoy - mailto:decoy_at_iki.fi, tel:+358-50-5756111
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