List the employees who have not showed up in any circulation history of documents. List the employee's name.
SELECT employee_name FROM Employees EXCEPT SELECT Employees.employee_name FROM Employees JOIN Circulation_History ON Circulation_History.employee_id = Employees.employee_id
employees who have not showed up in any circulation history of documents refers to selecting employees not present in Circulation_History; list the employee's name refers to selecting employee_name;