Employees whose manager left the company

#
# Table: Employees
# +-------------+----------+
# | Column Name | Type     |
# +-------------+----------+
# | employee_id | int      |
# | name        | varchar  |
# | manager_id  | int      |
# | salary      | int      |
# +-------------+----------+
# In SQL, employee_id is the primary key for this table.
# This table contains information about the employees, their salary, and the ID of their manager. Some employees do not have a manager (manager_id is null).
# Find 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 result format is in the following example.
# Example 1:
# Input:
# 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  |
# +-------------+-----------+------------+--------+
# Output:
# +-------------+
# | employee_id |
# +-------------+
# | 11          |
# +-------------+
# Explanation:
# 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.
#

# Write your MySQL query statement below

SELECT employee_id
FROM Employees
WHERE salary < 30000
  AND manager_id IS NOT NULL
  AND manager_id NOT IN (SELECT employee_id FROM Employees)
ORDER BY employee_id;