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From: zeldorblat@gmail.com
Newsgroups: comp.databases.theory
Subject: Re: Storing "deleted" data
Date: 31 Oct 2005 07:02:21 -0800
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Xref: dp-news.maxwell.syr.edu comp.databases.theory:34151

>b)You can try to declare a foreign key reference to one table AND another.

That doesn't help, though.  Consider the following:

create table livePeople (
   personID int not null,
   ...
)

create table deadPeople (
   personID int not null,
   ...
)

create table personComment (
    personID int not null,
    commentID int not null
)

So what primary key does personComment.personID refer to?  As far as I
know, while it can refer to livePerson.personID AND
deadPerson.personID, it can't refer to livePerson.personID OR
deadPerson.personID.  Furthermore, there's no way to indicate that
livePerson.personID and deadPerson.personID have to be unique when
combined.