$1.$ Retrieve the social security numbers of all employees who work on project number $1,2,$ or $3.$ Use two methods, IN clause and OR conditions

$2.$ List the first name and last name of employees who do not work on any project

$3.$ Create a report showing total hours worked by each employee

$4.$ Retrieve the name and address of employees who work for the 'Research' department. Use three different approaches. Use a Non nested, a Nested and a Join approaches

$5.$ List the names of projects that involve an employee whose last name is 'Smith' as a worker or as a manager of the department that controls the project. Use nested and no nested approach

$6.$ List the names of employees whose salary is greater than the salary of all managers

$7.$ Retrieve the top $5$ employees with the highest salaries

$8.$ Find the sum of the salaries, maximum salary, minimum salary, and average salary of employees in the $$Research$$ department

$9.$ Count the number of employees who work for the 'Research' department

$10.$ Find employees who work on more than one project

$11.$ Count the number of employees in Department number $3$ who have worked on at least one project

$12.$ For each department, retrieve the department number, the number of employees in the department, and their average salary

$13.$ For each project, retrieve the project number, project name, and the number of employees who work on that project

$14.$ For each project, retrieve the project number, project name, and number of employees from department $3$ who work on the project

$15.$ For each project that has more than one employee work, retrieve the project number, project name, and the number of employees who work on that project.

$16.$ For each department that has more than $1$ employee, retrieve the department name and the number of employees who are making more than $$50,000$