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

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"