Module Overview

What You’ll Learn

• Design related tables
• Implement foreign keys
• Maintain referential integrity
• Model real-world relationships

💡 Why this module matters: Real data is rarely one flat table, an order belongs to a customer, a product belongs to a category. This module covers how to model those connections correctly, before the next module covers how to actually query across them.

What’s Covered

• One-to-One, One-to-Many, and Many-to-Many relationships, the three shapes a relationship can take.
• Foreign keys, the mechanism that actually enforces a relationship.
• Composite primary keys, a primary key made of more than one column.
• Junction tables, how a many-to-many relationship is actually implemented.
• Referential integrity, keeping related data consistent.
• ON DELETE and ON UPDATE actions, what happens to related rows when the row they point to changes or disappears.

Hands-On

By the end of this module, you’ll build related tables, create foreign keys, implement a many-to-many relationship with a junction table, and test cascading actions for yourself.

Next module puts these relationships to work, querying across multiple tables at once with every type of JOIN.