RelationalDBDesign
RelationalDBDesign

Third Normal Form
«Prev
Next»

## How to eliminate Transitive Dependencies

### First, Second, and Third Normal Forms

Lesson 4 | Transitive dependencies in more Detail |

Objective | Explain How to eliminate Transitive Dependencies |

Putting set theory firmly to the side, there is a way to eliminate transitive dependencies. Make sure every relation refers to a single entity.

Here again, is the relation we have been examining in the last few lessons:

It refers to two business objects: Items and Categories. The*transitive dependency* in the relation, which is in 2NF, causes the relation to have the same problems as a relation that is only in 1NF.

Here again, is the relation we have been examining in the last few lessons:

Item (ItemNo, Title, Price, CategoryID, CategoryName, CategoryManager)

It refers to two business objects: Items and Categories. The

- You must know one item in a category to enter information about that category.
- Deleting a record referring to the only item in a category deletes all information about that category.

Separating the relation into two relations:

Item (ItemNo, Title, Price, CategoryID) and Category (CategoryID, CategoryName, CategoryManager)

removes the transitive dependency. The relation is now in 3NF.

Remember that the relations must be linked by a common field and in this case it is CategoryID.

The next lesson summarizes the process for achieving third normal form and asks you to determine whether relations are in 3NF and to translate relations from 2NF into 3NF.

The next lesson summarizes the process for achieving third normal form and asks you to determine whether relations are in 3NF and to translate relations from 2NF into 3NF.

Before moving to the next lesson, click the link below to read about the requirements of

- first,
- second,
- and third normal forms