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Data Analysis for Database Design, 3rd Edition
book

Data Analysis for Database Design, 3rd Edition

by David Howe
May 2001
Intermediate to advanced content levelIntermediate to advanced
336 pages
14h 36m
English
Butterworth-Heinemann
Content preview from Data Analysis for Database Design, 3rd Edition
Properties of relationships
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An important property of a relationship is its degree. Suppose there is a relationship
Teaches between the entities Lecturer and Course; a lecturer is identified by
lecturerName, and a course by courseNo. There are three possible kinds of relationship
degree, each corresponding to different pairs of enterprise rules for the relationship.
1:1 relationship
Enterprise rules:
‘A lecturer teaches, at most, one course.’
‘A course is taught by, at most, one lecturer.’
This pair of enterprise rules defines Teaches as being a 1:1 relationship. (Read 1:1 as
1-to-1.) A typical occurrence diagram is shown ...
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Publisher Resources

ISBN: 9780750650861