What is Normalization?
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. By dividing data into smaller, related tables, normalization ensures that:

Each piece of data is stored only once.
The database is easier to maintain and update.

Why Normalize a Database?

Reduces Redundancy: Eliminates duplicate data.
Improves Consistency: Ensures that changes in one place are reflected everywhere.
Saves Space: Minimizes storage requirements.
Makes Queries Easier: Simplifies complex queries by structuring data logically.

Understanding the Normal Forms

Normalization involves applying a series of rules, known as normal forms. Here’s a quick overview of the first three:

  • First Normal Form (1NF): Eliminate duplicate columns and ensure each field contains atomic (indivisible) values.
ID Name PhoneNumbers
1 Alice 123-456-7890, 555-555-5555

After 1NF:

ID Name PhoneNumber
1 Alice 123-456-7890
1 Alice 555-555-5555
  • Second Normal Form (2NF): Ensure all non-key columns depend only on the primary key.

Example: Split data into separate tables when attributes don’t fully depend on the primary key.

  • Third Normal Form (3NF): Remove transitive dependencies (i.e., non-key columns depending on other non-key columns).

Example: Breaking Down a Table
Unnormalized Table (UNF):

OrderID CustomerName ProductName Price CustomerEmail
101 Alice Laptop 800 [email protected]
102 Bob Phone 500 [email protected]

After Normalization (3NF):

customers Table:

CustomerID Name Email
1 Alice [email protected]
2 Bob [email protected]

orders Table:

OrderID CustomerID ProductName Price
101 1 Laptop 800
102 2 Phone 500

Challenge: Normalize This

Scenario: You’re given the following table:

EmployeeID Name Department DepartmentLocation ManagerName
1 Alice HR New York John Smith
2 Bob HR New York John Smith
  • Identify redundancies.
  • Create separate tables to normalize the data to 3NF.

Think About It
Are there situations where you might not want to normalize (e.g., analytics databases)?
How do you balance normalization with query performance?