To find employees whose manager works in a different department, you can use a subquery or a join that compares the DEPARTMENT_ID of the employee with the DEPARTMENT_ID of their manager.
A). This query is incorrect because the NOT IN subquery incorrectly attempts to compare EMPLOYEE_ID with MANAGER_ID, and the correlation condition inside the subquery is incorrect.
B). This query is correct. The NOT EXISTS clause correctly identifies employees whose MANAGER_ID matches the EMPLOYEE_ID of another employee (mgr) and where the DEPARTMENT_ID differs from that manager's DEPARTMENT_ID.
C). This query is incorrect because the LEFT JOIN will return all employees, and there is no WHERE clause to filter out those employees whose managers are in the same department.
D). This query is incorrect. The RIGHT JOIN does not ensure that the resulting rows are for employees whose manager works in a different department. It also returns all managers, which is not the requirement.
E). This query is correct. The JOIN ensures that the returned rows are for employees (emp) whose MANAGER_ID matches the EMPLOYEE_ID of managers (mgr), and it correctly filters to include only those employees whose DEPARTMENT_ID is different from their manager's DEPARTMENT_ID.