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4. Database Design Principles > 4.3. First Normal Form

First Normal Form

First normal form is very simple. A table scheme is said to be in first normal form if the attribute values are indivisible. To illustrate, we considered in Chapter 1 the question of including all the authors of a book in a single attribute, called Authors. Here is an example entity:

ISBN = 0-55-123456-9
Title = Main Street
Authors = Jones, H. and Smith, K.
Publisher = Small House

Since the table scheme in this case allows more than one author name for the Authors attribute, the scheme is not in first normal form. Indeed, one of the obvious problems with the Authors attribute is that it is impossible to sort the data by individual author name. It is also more difficult to, for instance, prepare a mailing label for each author, and so on.


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