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.
Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.