How many people work in the Sales department?

SELECT COUNT(*)
FROM
    employee e
INNER JOIN
    department d ON e.department = d.id
WHERE d.dept_name = 'Sales';

List the names of all employees assigned to the 'Plan Christmas party' project

SELECT e.emp_name as Employee_Name, p.project_name
FROM
    employee e
INNER JOIN
    employee_project ep ON e.id = ep.emp_id
INNER JOIN
    project p ON p.id = ep.project_id
WHERE p.project_name = 'Plan christmas party';

List the names of employees from the Warehouse department that are assigned to the 'Watch paint dry' project.

SELECT e.emp_name as Employee_Name, p.project_name
FROM
    employee e
INNER JOIN
    department d ON d.id = e.department
INNER JOIN
    employee_project ep ON e.id = ep.emp_id
INNER JOIN
    project p ON p.id = ep.project_id
WHERE p.project_name = 'Watch paint dry' AND d.dept_name = 'Warehouse';

Which projects are the Sales department employees assigned to?

SELECT p.project_name
FROM
    employee e
INNER JOIN
    department d ON d.id = e.department
INNER JOIN
    employee_project ep ON e.id = ep.emp_id
INNER JOIN
    project p ON p.id = ep.project_id
WHERE d.dept_name = 'Sales';

List only the managers that are assigned to the 'Watch paint dry' project.

SELECT e.emp_name as Employee_Name, p.project_name
FROM
    employee e
INNER JOIN
    department d ON d.manager = e.id
INNER JOIN
    employee_project ep ON e.id = ep.emp_id
INNER JOIN
    project p ON p.id = ep.project_id
WHERE p.project_name = 'Watch paint dry';