SQL Joins Explained: INNER, LEFT, RIGHT & FULL OUTER

Two tables, one wider result. This episode of Zero to Pro breaks down how SQL joins actually work: matching rows on a related column, the strict all-or-nothing behavior of INNER JOIN, how LEFT/RIGHT/FULL OUTER JOIN keep unmatched rows and fill them with NULL, the classic gotcha where a WHERE clause silently turns your LEFT JOIN back into an INNER JOIN, self joins for hierarchical data like an employee/manager table, and what the query engine is actually doing under the hood with hash joins and nested loops. TIMESTAMPS 00:00 Intro 00:19 What Is a Join? 00:38 INNER JOIN 00:57 LEFT / RIGHT / FULL OUTER JOIN 01:27 The Gotcha — ON vs WHERE 02:02 Self Join 02:24 How the Engine Joins Rows 02:58 Recap