CREATE TABLE captain (Captain_ID NUMBER, Name CLOB, Ship_ID NUMBER, age CLOB, Class CLOB, Rank CLOB)
CREATE TABLE Ship (Ship_ID NUMBER, Name CLOB, Type CLOB, Built_Year FLOAT, Class CLOB, Flag CLOB)

For those ships that do not have a captain, tell me the proportion of their classes using a pie chart.
SELECT Class, COUNT(Class) FROM Ship WHERE NOT Ship_ID IN (SELECT Ship_ID FROM captain) GROUP BY Class
SELECT "Class", COUNT("Class") FROM "Ship" WHERE NOT "Ship_ID" IN (SELECT "Ship_ID" FROM "captain") GROUP BY "Class"