Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!natinst!bloom!bobd
From: bobd@bloom.UUCP (Bob Donaldson)
Newsgroups: comp.databases
Subject: Re: Entity Supertypes/Subtypes & SQL
Summary: me too
Message-ID: <614@bloom.UUCP>
Date: 14 Apr 89 01:57:45 GMT
References: <1015@cetc.Wichita.NCR.COM>
Lines: 75

In article <1015@cetc.Wichita.NCR.COM>, sjohnson@cetc.Wichita.NCR.COM (Steve Johnson) writes:
> >In message <1011@cetc.Wichita.NCR.COM>, sjohnson@cetc.Wichita.NCR.COM writes:
> 
> >>I   am   looking  for  a  solution  to   the   following   entity 
> >>supertype/subtype problem.
> 
> >[Example of Purchase Orders dealing with <Animal, Vegetable, Mineral>
> > items - seems a variation on the Factory Model - see below]
>
> >The problem requires some tradeoffs.  With the relations as defined, it
> >is fairly easy to design applications that can determine PO for minerals,
> >etc., but it is very difficult to get information about a PO of a certain
> >date.  The connections between relations are dependent upon values of
> >tuples within relations.  The relational model supports fixed
> >relationships.            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>  ^^^^^^^^^^^^^^            
>  Isn't this rather large problem with the relational model 
>  considering that Entity Supertypes/Subtypes are as I see it
>  rather common.
>  Or was the relational model intended to be this way?
> 
> Does anyone have any neat routines written out there in Oracle using 
> cursors that handle querying different tables based on the result 
> of a column in a table?
> 
Me Too!!  I would be interested in such a routine for any SQL-based DBMS,
especially Oracle or Empress.

-=-
Bob Donaldson              ...!cs.utexas.edu!natinst!radian!bobd
Radian Corporation                    ...!sun!texsun!radian!bobd
PO Box 201088       
Austin, TX  78720       (512) 454-4797

Views expressed are my own, not necessarily those of my employer.


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