course content

Course Content

Relational Database and Normalization

Third Normal FormThird Normal Form

The rules for the Third Normal Form are:

  • It must meet the requirements of the Second Normal Form.
  • Any attributes that don't depend on the primary key, but instead rely on other non-key attributes, should be moved to a different table.

Sometimes, you might want to add a new attribute to a table. But doing so could bloat the table's size considerably, especially if these attributes aren't related to the primary key. Such additions are not logical!

Consider this example:

In this case, Designer Grade and Designer Country aren't really attributes of the Project. They're specific to the Designer. As in the previous example, if we were to remove the first row, we'd lose vital information about Robert Jarry's Designer Grade and Designer Country.

It's time to normalize!

Project and Designer tables

Great! We now have distinct tables for each entity:

  • The Project table with attributes specific to the project.
  • The Designer table with attributes specific to the designer.

question-icon

What are the rules of the Third Normal Form?

Select a few correct answers

Everything was clear?

Section 3. Chapter 4