Normalized Database Designs

Each of the following relational database designs is normalized to at least third normal form. Each design has at least one interesting feature that may help you as you design databases.

Magazine

This very simple design shows that a linking table can be expanded to contain more columns than just the foreign keys from the two parent tables. Notice that the subscription table has relationships with the magazine and subscriber tables like a linking table would have. However, the subscription table also includes additional columns.

Automobile Dealership

One interesting feature of this simple database design for an automobile dealership is the purchase table. The purchase table allows a single automobile to be purchased multiple times which often happens at a dealership when a customer buys a new automobile and then several years later trades in that automobile, and the dealership sells the automobile as a used vehicle to a different customer.

Business Directory

The business directory design contains a table with a self-relationship. Notice in the category table how the parent_id column is a foreign key that is connected to the category_id primary key in the same table.

Church Ward

Personal Finance Ledger