Can you please help to find out why in the video you are using the dept_emp table instead of the dept_manager table? SELECT e.emp_no AS employee_id, min(dm.dept_no) AS department_code, (SELECT emp_no FROM dept_manager WHERE emp_no = 110022) AS manager_id FROM employees e JOIN dept_manager dm ON e.emp_no = dm.emp_no WHERE e.emp_no <= 10020 GROUP BY e.emp_no ORDER BY e.emp_no;

Because we need to extract data about the department each employee is part of. This can only be fetched from the dept_emp table which contains (emp_no, dept_no, from_date, to_date) as you see in the following result set: If you used the dept_manager table, then you will instead be extracting the dept_no of the manager himself not the dept_no of the employee. I hope I was able to explain.