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@xxxxxxxxx> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
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