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.

Notes:

• I am using the ISBN Number as my key to the textbook file - I could have chosen to make my own id number and carry the ISBN number on the file - in this case, it would have been a candidate key
• I only have one field for University/Company - if I wanted to carry multiple credentials I would set up a field with the key of author id# and credential to carry the information
• I need to have additional files to relate publishing company id # into to get the information about the publishing company and to relate agent code into to get agent information the publishing company id # and the agent code on the files above are foreign keys which will link into the primary key on the files below to access information.