Schema: CREATE TABLE Documents_to_be_destroyed (employee_id VARCHAR, Destruction_Authorised_by_Employee_ID VARCHAR); CREATE TABLE Employees (employee_id VARCHAR, Destruction_Authorised_by_Employee_ID VARCHAR)
Question: Show the ids of the employees who don't authorize destruction for any document.
SQL: SELECT employee_id FROM Employees EXCEPT SELECT Destruction_Authorised_by_Employee_ID FROM Documents_to_be_destroyed