Self Joins
Self Joins
March 28, 2025
A SQL self join joins a table with itself.
For example given the employee table below, write a SQL query that finds
out employees who earn more than their managers.
For the table, Joe is the only employee who earns more than his manager.
+----+-------+--------+------------+
| id | name | salary | manager_id |
+----+-------+--------+------------+
| 1 | joe | 70000 | 3 |
| 2 | henry | 80000 | 4 |
| 3 | sam | 60000 | NULL |
| 4 | max | 90000 | NULL |
+----+-------+--------+------------+Answer:
SELECT a.name AS employee
FROM employee AS a
JOIN employee AS b on a.manager_id = b.id
WHERE a.salary> b.salary