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Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!tektronix!Dale Brayden <daleb>
From: Dale@tektronix.UUCP
Newsgroups: net.database
Subject: semantics of QBE
Message-ID: <6403@tektronix.UUCP>
Date: Thu, 30-Jan-86 13:05:39 EST
Article-I.D.: tektroni.6403
Posted: Thu Jan 30 13:05:39 1986
Date-Received: Sat, 1-Feb-86 05:43:49 EST
Sender: daleb@tektronix.UUCP
Organization: Tektronix, Beaverton OR
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	I am looking for a statement of the formal semantics of QBE. I
	have read the paper "Query-by-Example: a data base language" by
	M.M. Zloof (IBM Syst. J., #4, 1977) which is one of the early
	published descriptions of QBE. That paper presents QBE by
	means of (what else!) examples. That's sufficient for the easy
	cases, but I'm uncertain of the meaning of queries involving
	aggregates or (in Ingres terminology) aggregate functions.
	And queries that involve joins on sets are completely unclear
	to me.

	There is a paper entitled "Algorithm for Processing Query by
	Example" by Niebuhr et al (IBM Tech. Disc. Bull., vol. 19 #2)
	which helps a little, but assumes the reader already understands
	the semantics.

	Anyway, any pointers to papers will be muchly appreciated.

	Dale Brayden
	Scientific Computer Center, DS 50-454
	Tektronix, Inc.
	P.O. Box 500
	Beaverton, OR  97077