Re: 3 value logic. Why is SQL so special?

David Portas wrote:
> Cimode wrote:
> > A UNION equivalent an LEFT OUTER JOIN BULLSHIT!!!. A LEFT OUTER JOIN is
> > just SQL miserable way to force a presentation inspired perspective
> > into design issues that should be regulated by normalization to
> > preserve integrity. The proof is that you can do a UNION using 2
> > relations but using LEFT OUTER JOIN when dealing with relations has no
> > meaning. Consider 2 tables table1(id1, key1) and table2(id2, key2)
> >
> > Table1
> > 1, A
> > 2, B
> > 3, C
> >
> > Table2
> > 8, A
> > 10, C
> >
>
> T1{k,i1,i2} UNION (T1{k,i1} JOIN T2{k,i2})
>
> Obviously some suitable value or expression has to be supplied for i2
> on the left hand side of the UNION.
Not the point. A UNION has nothing to do with a JOIN. They are both separate operators applyable on relations. Trying to prove that one is derived from another is just
meaningless, the same way you would try to derive a DIVIDE operator with a PLUS operator...This is a dead end.

> David Portas
Received on Sat Sep 16 2006 - 22:10:32 CEST