Re: What to call this operator?

From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 1 Jul 2005 08:09:24 -0700
Message-ID: <1120230564.593323.241990@g43g2000cwa.googlegroups.com>

Jon Heggland wrote:
> In article <1120069466.357430.273600_at_o13g2000cwo.googlegroups.com>,
> marshall.spight_at_gmail.com says...
> > With join, all keys are preserved.
>
> Umm... they are? What do you mean by "preserved"? Perhaps I
> misunderstand you, but a key of one of the operands is not necessarily a
> key of the result.

Okay. What rule would you propose?

In fact, since I proposed that rule in the above-referenced message, I did think of a counterexample which would make some relations unjoinable, which isn't good.)

Marshall Received on Fri Jul 01 2005 - 10:09:24 CDT