Lab schema (HR schema) is listed as below (primary keys are underlined):

Regions(region_id, region_name);
Countries(country_id, country_name, region_id);
Locations(location_id, street_address, postal_code, city, state_province, country_id);
Departments(department_id, department_name, manager_id, location_id);
Jobs(job_id, job_title, min_salary, max_salary);
Employees(employee_id, first_name, last_name, email, phone_number, hire_date, job_id, salary, commission_pct, manager_id, department_id);
Job_History(employee_id, start_date, end_date, job_id, department_id);

• Aggregation Queries

Write a single SQL query for each of the following questions.

1. For each country, count the number of departments located in that country. List the name of the country and the count as numOfDepartments. If no department is there, the count should be shown as 0.
2. List the name of each department that has more than 20 employees working in it.
3. For each department whose human resource cost (sum of salary of each employee working in it) is greater than or equal to $40,000, list the department's name, the total salary and the average salary of the department.
4. Find the department with the most people working in it. List the department's name.
   • Using aggregation function max
   • Without using max, using operator against a set instead
5. List the name of each employee who has more than 5 employees directly report to him/her.
   • Using having clause
   • Using subquery in the from list