Question: What are the names, details and data types of the characteristics which are never used by any product?
SQL: SELECT characteristic_name, other_characteristic_details, characteristic_data_type FROM CHARACTERISTICS EXCEPT SELECT t1.characteristic_name, t1.other_characteristic_details, t1.characteristic_data_type FROM CHARACTERISTICS AS t1 JOIN product_characteristics AS t2 ON t1.characteristic_id = t2.characteristic_id