Employees Whose Manager Left the Company

Write an SQL query to report the IDs of the employees whose salary is strictly less than $30000 and whose manager left the company. 
When a manager leaves the company, their information is deleted from the Employees table, but the reports still have their manager_id set to the manager that left.
Return the result table ordered by employee_id.
The query result format is in the following example.

Employees table:
+-------------+-----------+------------+--------+
| employee_id | name      | manager_id | salary |
+-------------+-----------+------------+--------+
| 3           | Mila      | 9          | 60301  |
| 12          | Antonella | null       | 31000  |
| 13          | Emery     | null       | 67084  |
| 1           | Kalel     | 11         | 21241  |
| 9           | Mikaela   | null       | 50937  |
| 11          | Joziah    | 6          | 28485  |
+-------------+-----------+------------+--------+

Result table: 
+-------------+
| employee_id |
+-------------+
| 11          |
+-------------+

The employees with a salary less than $30000 are 1 (Kalel) and 11 (Joziah).
Kalel's manager is employee 11, who is still in the company (Joziah).
Joziah's manager is employee 6, who left the company because there is no row for employee 6 as it was deleted.



Answer:

SELECT EMPLOYEE_ID
FROM EMPLOYEES
WHERE SALARY < 30000
AND MANAGER_ID NOT IN (SELECT EMPLOYEE_ID FROM EMPLOYEES)
ORDER BY EMPLOYEE_ID
;