Re: Relational symmetric difference is well defined
From: Marshall <marshall.spight_at_gmail.com>
Date: 29 May 2007 14:47:59 -0700
Message-ID: <1180475279.677392.228870_at_z28g2000prd.googlegroups.com>
Date: 29 May 2007 14:47:59 -0700
Message-ID: <1180475279.677392.228870_at_z28g2000prd.googlegroups.com>
On May 11, 10:56 am, Vadim Tropashko <vadimtro_inva..._at_yahoo.com>
wrote:
> Symmetric difference identity
>
> (A \ B) \/ (B \ A) = (A \/ B) \ (B /\ A)
>
> holds in relational lattice.
Other symmetric differences:
(A /\ B) \ (A \/ B)
Produces an empty relation with the symmetric difference
of the attributes of A and B. (Symmetric difference of
columns, no rows.)
(A \/ B) \ (A /\ B)
Produces 01 if A and B have attributes in common
that have values that are not in common; 00 otherwise.
(Symmetric difference of rows; no columns.)
(Same as both sides of OP's equation.)
Marshall Received on Tue May 29 2007 - 23:47:59 CEST