Module Overview

What You’ll Learn

• Combine data from multiple tables
• Choose appropriate join types
• Write multi-table queries

💡 Why this module matters: Module 9 covered how tables relate, this one covers how to actually ask a question that spans them, “which customer placed each order,” “which products belong to which category,” in a single query.

What’s Covered

• INNER JOIN, matching rows that exist in both tables.
• LEFT JOIN and RIGHT JOIN, keeping every row from one side, matched or not.
• FULL JOIN, keeping every row from both sides.
• CROSS JOIN, every combination of rows from both tables.
• SELF JOIN, joining a table to itself.
• Table aliases, keeping multi-table queries readable.
• Joining multiple tables, combining more than two tables in one query.

Hands-On

By the end of this module, you’ll join customers and orders, join products and categories, self-join an employee hierarchy, and build multi-table reports.

Next module goes further still, subqueries, CTEs, and conditional logic for questions a single flat query can’t answer.