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

I want to know the proportion of the average age for each class.
SELECT Class, AVG(age) FROM captain GROUP BY Class
SELECT "Class", AVG("age") FROM "captain" GROUP BY "Class"