Re: 8.2 contrib. "Full Disjunction"

"Martijn van Oosterhout" <kleptog(at)svana(dot)org> writes:

> On Fri, Jun 22, 2007 at 07:38:01PM +0300, Tzahi Fadida wrote:
>> Let me simplify it in lamer terms.
>> Basically, you have a cycle in your relations schema. i.e.
>> rel A: att-x, att-y
>> rel B: att-y, att-z
>> rel C: att-z, att-x
>>
>> The only way to join these three without loosing a lot of information (aside
>> from some very weird corner cases which i won't mention here), is to use my
>> full disjunctions which is probably most certainly the only implementation of
>> the operation in existence to calculate the general case (which you can see
>> above).
>
> FWIW, with this simple description I finally worked out what full
> disjunctions are and why you can't do them (efficiently) in SQL.

I'm still lost. I can see how it would be hard to join these together but I'm
not sure what result I would be after.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com