Relational databases deliberately split information across multiple tables to avoid duplication: customers live in one table, orders in another, products in a third. That design keeps data clean, but it means almost every useful question you ask will require pulling columns from more than one table at a time. JOINs are the SQL mechanism that makes this possible, matching rows from one table to rows in another based on a shared key.
In this topic you will work through the four primary JOIN types. An INNER JOIN returns only rows that have a match on both sides. A LEFT JOIN keeps every row from the left table and fills in NULLs where no match exists on the right; a RIGHT JOIN does the mirror image; and a FULL JOIN preserves unmatched rows from both tables. The differences matter enormously in practice — the same query written with INNER instead of LEFT can silently drop the customers who have not yet placed an order, which is often exactly the group you were trying to count.
As you watch the videos below, pay close attention to three things: the join condition (the ON clause and which columns it compares), where NULLs appear in the result set and why, and how table aliases keep multi-table queries readable. When a video shows a diagram or animation, try to connect the picture back to the actual rows in the result table rather than memorizing the shape alone. Then practice writing the queries yourself — JOIN syntax becomes intuitive quickly once you have typed a dozen of them.
A guided walkthrough of SQL JOINs with worked examples, covering what a JOIN does and how the major types differ in the rows they return. Based on the title and channel, expect coverage of INNER, LEFT, RIGHT and FULL joins with sample tables and result sets, plus the ON clause syntax that drives the match.
Database Star is a well-established SQL instruction channel, and at roughly 11 minutes this video gives enough room to treat each JOIN type properly rather than rushing — making it a solid primary overview for the first six subtopics.
An animated tour of six JOIN variations, including the four core types plus additional forms such as cross and self joins. The description includes Docker and SQL commands so you can spin up a database and run the same statements yourself while watching.
The animations make the matched-versus-unmatched row behavior visually concrete, which is the single hardest idea in this topic, and the included practice commands let you verify each JOIN's output with your own hands.
A short, focused lesson on extending JOIN syntax beyond two tables, showing how to chain multiple JOIN clauses in a single SELECT statement. Expect discussion of the order in which tables are joined and how each successive ON condition links back to the growing result set.
This directly addresses the Writing Multi-Table Queries with JOINs subtopic, which the two-table examples do not fully cover, and it comes from the same instructor as the overview video so the notation stays consistent.
Together these three videos map closely onto MO1. The Database Star overview and the animated comparison both lay out INNER, LEFT, RIGHT and FULL JOIN side by side so you can distinguish them by the rows each returns, while the examples in all three videos model the judgment of choosing the appropriate JOIN for a given retrieval scenario. The three-table video then extends that skill from pairs of tables to the realistic multi-table queries this module expects you to write. These videos are deliberately scoped to JOINs; the filtering and aggregation outcomes (MO2 through MO5) are addressed by the other resources in this module, though you should expect WHERE clauses to appear alongside the JOIN examples here.
These videos were chosen from YouTube on October 2, 2026. Each has captions; the player turns them on. Videos on YouTube can be changed or removed — if one no longer plays, tell your instructor. If a player does not appear, use its Watch on YouTube link.