Question: Find the last name of the students who currently live in the state of North Carolina but have not registered in any degree program.
SQL: SELECT T1.last_name FROM Students AS T1 JOIN Addresses AS T2 ON T1.current_address_id  =  T2.address_id WHERE T2.state_province_county  =  'NorthCarolina' EXCEPT SELECT DISTINCT T3.last_name FROM Students AS T3 JOIN Student_Enrolment AS T4 ON T3.student_id  =  T4.student_id