Third Normal Form
The third normal form denotes that there must not be any dependency among non-key attributes. Resolving the above we get,
Invoice_Master Invoice_Item Item_Master
Invoice_code Invoice_No Item_code
Inv_date item_code description
Order_code description rate
Invoice_Value ord_qty
Ord_value
Order_Cust Customer_Master
Order_code cust_code
Cust_code cust_name
Order_date address
Third normal form is achieved when transitive dependencies are erased from a record design. A number of the non-key attributes are dependent not only on the primary key but also on a non-key attribute. That’s referred to as a transitive dependency.
![1935_Third Normal Form.png](https://www.expertsmind.com/../CMSImages/1935_Third Normal Form.png)
Conversion to 3rd normal form removes transitive dependence through splitting the association into two relations.
![2098_Third Normal Form 1.png](https://www.expertsmind.com/../CMSImages/2098_Third Normal Form 1.png)
Motivation for concern. When there is a transitive dependence the deletion of A will cause deletion of B and C as well.
•A, B and C are three data items in a record
•If functionally dependency of C is on B and
•B is functionally dependent on A
•Then C is functionally dependent on A
•Thus, a transitive dependency exists.
It is also in third normal form because there are no transitive dependencies.