CREATE TABLE employees (department_id VARCHAR2, manager_id VARCHAR2, employee_id VARCHAR2)

Find the ids of the departments where any manager is managing 4 or more employees.
SELECT DISTINCT department_id FROM employees GROUP BY department_id, manager_id HAVING COUNT(employee_id) >= 4
SELECT DISTINCT "department_id" FROM "employees" GROUP BY "department_id", "manager_id" HAVING COUNT("employee_id") >= 4