Re: Clean Object Class Design -- What is it?

What should be used for a primary key in a relational design? Is it better to use real-world values (e.g. SSN, although this would only work for US employees) or is it better to generate a key?

Does the RDBMS always create an index on a primary key to ensure uniqueness? If this is the designer's responsibility, do all tables in a database generally have primary keys with uniqueness constraints defined, or is that "overkill" for practical purposes?

How is generating a key better than the ODBMS equivalent of a system-generated Oid?

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Cheers
Steve (steve at wart dot ca ICQ 50919689)