What are the different types of JOINs in MySQL?

Question

Accepted Answer

JOINs combine rows from two tables based on a related column. The choice of JOIN decides which rows survive when there's no match. INNER JOIN — only rows with a match in both tables. The default and most common. LEFT JOIN — all rows from the left table; matched columns from the right, NULL where no match. RIGHT JOIN — mirror of LEFT JOIN; rare since you can flip table order. FULL OUTER JOIN — all rows from both sides; not supported in MySQL — emulate with UNION of LEFT and RIGHT. CROSS JOIN — cartesian product; every row of A paired with every row of B. SELF JOIN — joining a table to itself with aliases; for hierarchies and pair comparisons. Know all 6 types: INNER, LEFT, RIGHT, FULL OUTER (simulated), CROSS, SELF. The LEFT JOIN + WHERE IS NULL pattern for finding unmatched rows is very commonly asked. SELF JOIN for employee/manager hierarchy. MySQL has no native FULL OUTER JOIN — simulate with UNION.