MySQL Normalization: Theory and Practice for Interview Success

Introduction to Normalization

Database normalization is a systematic approach to organizing data in a relational database that eliminates redundancy and ensures data integrity. Created by Edgar F. Codd in the 1970s, normalization consists of several "normal forms" that represent increasingly stringent rules for database design.

Why Normalization Matters

In real-world applications, proper normalization offers critical benefits:

  1. Eliminates data redundancy: Reduces storage requirements and prevents update anomalies
  2. Ensures data integrity: Reduces the risk of inconsistent data
  3. Simplifies maintenance: Makes it easier to modify database structures
  4. Improves query performance: For many transaction-processing scenarios

The 9-Step Normalization Process

Step 1: Identify Entities and Attributes

Determine all real-world entities and their properties.

Real-world example: An e-commerce platform needs to track customers, products, orders, and payments.

Customer: customer_id, name, email, phone, address, city, state, postal_code
Product: product_id, name, description, price, category, stock_quantity
Order: order_id, customer_id, order_date, shipping_address, total_amount

Step 2: Create Initial Tables with Primary Keys

Define tables and ensure each has a unique identifier.

CREATE TABLE customers (
    customer_id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100),
    email VARCHAR(100),
    phone VARCHAR(20),
    address TEXT,
    city VARCHAR(50),
    state VARCHAR(30),
    postal_code VARCHAR(20)
);

Step 3: Apply First Normal Form (1NF)