UNIQUE &NOT NULL vs PK

could someone list out the advantages/disadvantages of defining a column with PRIMARY KEY constraint over UNIQUE and NOT NULL constraint?

i am wondering where the diff. between these two exists?

... in storage of the constraint ???
... ability to be REFERENCEd in foreign tables ???
... INDEXabilty ???
... or something else ???

thanks in advance for your valuable responses. regards
Nanda

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Before you buy. Received on Mon Nov 08 1999 - 10:57:51 CST