Example of third normal form using a text book company:

The textbook company that we are looking at keeps the following information:

ISBN number

Name of textbook

Name of author(s) - frequently there is no primary author

Date of publication

Price of textbook

Publishing company for book

Address/phone etc. information about publishing company

University, company or other credential

Email address for author

Authors current agent

Email address for agent

Address/phone etc. for agent

I'm sure there is information that I am missing, but this is enough to make the points I want to make.

The first problem that we face is that one textbook can have many authors and one author can write many textbooks. This means that textbooks and authors are in a many to many relationship. I can't carry the information about all the authors in the textbook file and be in first normal form and I can't carry information about all of the textbooks in the authors file and be in third normal form. Therefore I am going to use what I call a bridge file to link the authors and the texts.

Textbook File

Bridge File

Author File

ISBN Number = KEY

ISBN Number} = KEY

Author id #

Author id # = KEY

Name of textbook

Author Name

Date of publication



Price of textbook


Email address

Publishing company id #


Agent code



Publishing Company File

Agent File


Publishing Company Id # = KEY

Agent code = key

Company Name

Agent Name


Agent address