Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!fciva!dag
From: dag@fciva.FRANKLIN.COM (Daniel A. Graifer)
Newsgroups: comp.databases
Subject: Relational Database Question
Message-ID: <542@fciva.FRANKLIN.COM>
Date: 29 Aug 90 16:39:35 GMT
Reply-To: uunet!fciva!dag (Daniel A. Graifer)
Distribution: na
Organization: Franklin Mortgage Capital Corp., McLean, Va.
Lines: 51
Keywords:

I am trying to add the following capability to an existing Unify 4 database,
(but I think the question is valid in any implementation).  The existing
database contains a table of items identified by an itemkey.  I want to add
the ability to generate reports with items subtotaled in sets contained in
the database.  We should be able to store several such groups of item-sets.

TABLE items
	itemkey	*	STRING 6
	.
	.
	.

TABLE rptgrp
	grpname	*	STRING 6
	grpdesc		STRING 20

TABLE rptset
	setkey	*	COMB
	  setname	STRING 6		part of setkey
	  ofgrp		Ref to grpname	part of setkey
	setdesc		STRING 20

TABLE item2grp	/* Case 1 */
	i2gkey	*	COMB
	  item		Ref to itemkey	part of i2gkey
	  set		Ref to setkey	part of i2gkey

TABLE item2grp /* Case 2 */
	i2gkey	*	COMB
	  item		Ref to itemkey	part of i2gkey
	  grp		Ref to grpname	part of i2gkey
	set			Ref to setname
	
The first case doesn't correctly express the relationship:  Items must be
uniquely assigned within each group.  Case 1 would permit the assignment of
an item to two sets within the same group.

The second case permits an item to be assigned to a non-existant set/group
combination, ie one which doesn't occur in rptset.

One way of presenting the question is relative to Case 1:  How do I make
a subfield of the combined field 'set' part of the unique key for item2grp?

Any help greatly appreciated.
Dan
P.S. Reply to uunet.uu.net!fciva!dag.  My newsposter is editting my .signature
file into garbage!
-- 
Daniel A. Graifer			Franklin Mortgage Capital Corporation
uunet!dag@fmccva.franklin.com		7900 Westpark Drive, Suite A130
(703)448-3300				McLean, VA  22102