SELECT and joins

Joins combine rows across tables, and the join type decides what happens to the rows with no match. Most wrong result sets are a join type mistake.

What this lesson covers

• Choose between inner, left, right, and full joins
• Join on the right keys and avoid accidental fan-out
• Filter in WHERE versus in the join condition

This lesson sits in SQL Essentials, part of PostgreSQL for Developers. It assumes what came before it and leads directly into the next lesson in the module.