Re: what is union?

From: paul c <toledobythesea_at_oohay.ac>
Date: Sun, 13 Sep 2009 00:53:53 GMT
Message-ID: <BoXqm.43752$Db2.4349_at_edtnps83>



paul c wrote:
> Regarding so-called "union compatibility",.suppose relations A and B
> with equal headings, say named h. Suppose non-empty relation U with
> only one attribute that is not in any other heading.
>
> value i): A Join B projected on h, D&D style =
> (A <AND> B) {h}
> ...

Oops again, sorry, that expression should be (A <AND> B <AND> U) {h}. Received on Sat Sep 12 2009 - 19:53:53 CDT

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