What is the difference between INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, and CROSS JOIN?

Short answer: INNER returns matches only. LEFT keeps all left rows (NULL right when no match). RIGHT mirrors LEFT. FULL keeps unmatched from both. CROSS is Cartesian product. Be ready to write examples.

Sample solution

-- Employees without matching department (orphan check)
SELECT e.*
FROM Employees e
LEFT JOIN Departments d ON d.DepartmentId = e.DepartmentId
WHERE d.DepartmentId IS NULL;

Draw Venn diagrams verbally in 20 seconds — clarity scores points.