Database: products_gen_characteristics
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