Re: Relational symmetric difference is well defined
From: Jon Heggland <jon.heggland_at_idi.ntnu.no>
Date: Wed, 30 May 2007 08:27:19 +0200
Message-ID: <f3j5j3$r00$1_at_orkan.itea.ntnu.no>
Date: Wed, 30 May 2007 08:27:19 +0200
Message-ID: <f3j5j3$r00$1_at_orkan.itea.ntnu.no>
Marshall wrote:
> 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.)
So \ isn't antijoin after all? It removes attributes?
-- JonReceived on Wed May 30 2007 - 08:27:19 CEST