Database Concepts

Published by Pearson
ISBN 10: 0133544621
ISBN 13: 978-0-13354-462-6

Chapter 2 - The Relational Model - Review Questions: 2.11

Answer

Define the term nonunique key and give an example. A nonunique key not only identifies a row, but it potentially identifies more than one row. In the above example, we discussed the table: EXAMPLE: TEXTBOOK (ISBN, Title, Publisher, Copyright) In this case, a nonunique key would be Publisher. Many books are tied to the same publisher, so it cannot uniquely identify a row, and could be related to many rows in the table.

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