Second Normal form

Second Normal Form (2NF)

Definition

A table is in Second Normal Form (2NF) if it is in 1NF and all non-key attributes depend on the entire primary key.

Rules

• 1NF: The table must be in 1NF.
• No Partial Dependencies: No non-key attribute should depend on only one part of the primary key.

Benefits

• Eliminates Partial Dependencies: 2NF eliminates partial dependencies, reducing data redundancy.
• Improves Data Integrity: 2NF ensures that non-key attributes are dependent on the entire primary key.
• Simplifies Data Maintenance: 2NF makes data maintenance easier by reducing data redundancy.

Example

Consider a table that stores order information:

Order ID	Product ID	Product Name	Quantity
1	A	Product A	2

In this example, Product Name depends only on Product ID, which is a partial dependency. To convert this table to 2NF, we would create separate tables for orders and products:

Order ID	Product ID	Quantity
1	A	2

Product ID	Product Name
A	Product A