Understanding Database Normalization

Introduction to Database Normalization

Database normalization is the process of organizing the data in a database to minimize data redundancy and improve data integrity. There are several principles of database normalization, including first normal form (1NF), second normal form (2NF), and third normal form (3NF).

First Normal Form (1NF)

A table is in 1NF if each cell in the table contains a single value. For example, consider the following table:

Customer ID	Name	Orders
1	John Doe	Order 1, Order 2
2	Jane Doe	Order 3
This table is not in 1NF because the Orders column contains multiple values. To normalize this table, you can create a separate table for orders:
Customer ID	Order ID
---	---
1	1
1	2
2	3

Second Normal Form (2NF)

A table is in 2NF if it is in 1NF and each non-key attribute in the table depends on the entire primary key. For example, consider the following table:

Order ID	Customer ID	Order Date
1	1	2022-01-01
2	1	2022-01-15
3	2	2022-02-01
This table is not in 2NF because the Order Date column depends only on the Order ID column, not the Customer ID column. To normalize this table, you can create a separate table for orders:
Order ID	Order Date
---	---
1	2022-01-01
2	2022-01-15
3	2022-02-01

Third Normal Form (3NF)

A table is in 3NF if it is in 2NF and there are no transitive dependencies. For example, consider the following table:

Customer ID	Name	Salesperson
1	John Doe	Jane Smith
2	Jane Doe	John Smith
This table is not in 3NF because the Salesperson column depends on the Customer ID column, which depends on the Name column. To normalize this table, you can create a separate table for salespeople:
Salesperson ID	Name
---	---
1	Jane Smith
2	John Smith