3. Function

Find the number of employees

SELECT COUNT(super_id)
FROM employee;

Find the average of all employee's salaries

SELECT AVG(salary)
FROM employee;

Find the sum of all employee's salaries

SELECT SUM(salary)
FROM employee;

Find out how many males and females there are

SELECT COUNT(sex), sex
FROM employee
GROUP BY sex

Find the total sales of each salesman

SELECT SUM(total_sales), emp_id
FROM works_with
GROUP BY client_id;

Find the total amount of money spent by each client

SELECT SUM(total_sales), client_id
FROM works_with
GROUP BY client_id;