Question: Find the name of the ships that have more than one captain.
Schema: create table captain (ship_id varchar, PRIMARY KEY (ship_id)); create table ship (name varchar, ship_id varchar, PRIMARY KEY (name))
SQL: select t1.name from ship as t1 join captain as t2 on t1.ship_id = t2.ship_id group by t2.ship_id having count(*) > 1