Table with multiple fields as primary key?

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Author: Paolo Alexis Falcone
To: compsci
Subject: Table with multiple fields as primary key?
I've noticed in some of the clients that I've handled so far that
there's a practice of using more than one field for primary key (noted
by *), eg.


I'm assuming that the uniqueness quality still applies - if the
combination of the three keys would be unique then I think the data
would be accepted else it won't. But the said scenario can be
rewritten by making additional tables then making their primary keys
into foreign keys in another table, which would then be referred by
the table which originally used multiple fields for primary keys.

I'm still reviewing my database books, but isn't this what
normalization tries to avoid? I'm not certain if this is even proper
design - database theory does provide for multiple candidate keys in a
given relation but not more than one primary key.
Paolo Alexis Falcone
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