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)

What is the average age of captains in different classes?, and could you order in descending by the mean age please?
SELECT Class, AVG(age) FROM captain GROUP BY Class ORDER BY AVG(age) DESC
SELECT "Class", AVG("age") FROM "captain" GROUP BY "Class" ORDER BY AVG("age") DESC