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From: Erland Sommarskog <esquel@sommarskog.se>
Newsgroups: comp.databases.ms-sqlserver
Subject: Re: A question about relationship
Date: Tue, 11 Feb 2014 21:54:38 +0100
Organization: Erland Sommarskog
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Tony Johansson (johansson.andersson@telia.com) writes:
> Yes a customer without order sounds ok
> But order without customer is incorrect.
 
I would say that it depends on the business rules. :-) But, yes, it
would be a bit peculiar.

In Northwind CustomerID is nullable, although there is no such order 
in the data. Unfortunately, Northwind leaves a whole lot desired when it 
comes to nullability, indexes etc.

-- 
Erland Sommarskog, Stockholm, esquel@sommarskog.se