SELECT * FROM students CROSS JOIN courses; Result: 3 × 3 = 9 rows. A table joined with itself. Useful for hierarchical data (e.g., employee-manager).
📊 Intersection of A and B. 3.2 LEFT JOIN (or LEFT OUTER JOIN) Returns ALL rows from the left table, matched rows from the right table. NULL if no match. sql joins notes pdf
SELECT e.name, d.dept_name FROM employees e JOIN departments d ON e.dept_id = d.dept_id; Assume two tables: SELECT * FROM students CROSS JOIN courses; Result:
SELECT * FROM students INNER JOIN courses ON students.id = courses.student_id; | id | name | student_id | course | |----|-------|------------|---------| | 1 | Alice | 1 | Math | | 2 | Bob | 2 | Science | 📊 Intersection of A and B
| student_id | course | |------------|-----------| | 1 | Math | | 2 | Science | | 4 | Art | Returns only rows with matching keys in BOTH tables.
