LESSON 1.1
SELECT and joins
Learn key techniques and workflows in PostgreSQL for Developers.
5m
intermediate
11,890 students
Overview
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.
In this lesson you will:
- 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
Pro Tip
Use caching and revalidation wisely to ensure your app stays fast and data remains fresh without unnecessary requests.