July 2010
Intermediate to advanced
840 pages
16h 33m
English
Content preview from Joe Celko's SQL for Smarties, 3rd Edition
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2.1. Functional and Multivalued Dependencies
A normal form is a way of classifying a table based on the functional dependencies (FDs for short) in it. A functional dependency means that if I know the value of one attribute, I can always determine the value of another. The notation used in relational theory is an arrow between the two attributes, for example A → B, which can be read in English as “A determines B.” If I know your employee number, I can determine your name; if I know a part number, I can determine the weight and color of the part; and so forth.
A multivalued dependency (MVD) means that if I know the value of one attribute, I can always determine the values of a set of another attribute. The notation used in relational theory is ...
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