Yes.  Show the IDs of all employees who didn't destroy any documents please.
select employee_id from employees except select destroyed_by_employee_id from documents_to_be_destroyed
Thank you.  What are their names?
select employee_name from employees where employee_id in ( select employee_id from employees except select destroyed_by_employee_id from documents_to_be_destroyed )
Thank you.  What are their roles?
select role_code from employees where employee_id in ( select employee_id from employees except select destroyed_by_employee_id from documents_to_be_destroyed )
Yes.  What is their date of birth?
select date_of_birth from employees where employee_id in ( select employee_id from employees except select destroyed_by_employee_id from documents_to_be_destroyed )