SELECT name ,  CLASS FROM ship WHERE ship_id NOT IN (SELECT ship_id FROM captain)
Return the names and classes of ships that do not have a captain?
[Schema (values) (types)]: | ship_1 |  captain : captain_id (text) , name (number) , ship_id (text) , age (number) , class (text) , rank (text) | Ship : ship_id (text) , name (number) , type (text) , built_year (number) , class (text) , flag (text);