$1.$ Retrieve the names of employees who do not have supervisors

$2.$ Retrieve the names of employees who have supervisors

$3.$ Retrieve the social security numbers of all employees who work on project number $1,2,$ or $3.$ Use two different operators:

$1.$OR$$ Operator

$2.$IN$$ Operator

$4.$ List the first name and last name of employees who do not work on any project

$5.$ Retrieve the name and address of employees who work for the 'Research' department. Use three different approaches.

$1.$ a Non nested approach,

$2.$ a Nested approach

$3.$ a Join approach

$6.$ 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.

$1.$ Use nested and

$2.$ no nested approach

$7.$ List the names of employees whose salary is greater than the salary of all managers

$8.$ Retrieve the name of each employee who has a dependent with the same first name as the employee.

$9.$ Retrieve the name of each employee who has a dependent with the same name as the employee$$s first name.

$10.$ Retrieve the names of employees who have no dependents

$11.$ Retrieve the name of all employees and their supervisors

$12.$ Find the sum of the salaries, maximum salary, minimum salary, and average salary of employees in the $$Research$$ department

$13.$ Count the number of employees who work for the 'Research' department

$14.$ Count the number of employees in Department number $3$ who have worked on at least one project

$15.$ For each department, retrieve the department number, the number of employees in the department, and their average salary

$16.$ For each project, retrieve the project number, project name, and the number of employees who work on that project

$17.$ For each project, retrieve the project number, project name, and number of employees from department $3$ who work on the project

$18.$ 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.

$19.$ 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$