Re: Conjunction junction
From: Tony Andrews <andrewst_at_onetel.com>
Date: 1 Nov 2004 13:46:57 -0800
Message-ID: <1099345617.141898.319940_at_f14g2000cwb.googlegroups.com>
Date: 1 Nov 2004 13:46:57 -0800
Message-ID: <1099345617.141898.319940_at_f14g2000cwb.googlegroups.com>
Dan wrote:
> I'm not sure I agree. XOR could be a valid and useful logical
operator in
> conjunction with UNION. Even though the attribute in both relation
> "fragments" have the same name, and we
> presume to they have the same semantics, the fact that they are
qualified in
> two different relations makes the attributes distinguishable,
assuming of
> course that they are of the same type.
"XUNION" perhaps? Where (R1 XUNION R2) is equivalent to (R1 MINUS R2) UNION (R2 MINUS R1). Received on Mon Nov 01 2004 - 22:46:57 CET