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)

Plot the average of age by grouped by class as a bar graph, and show by the bar in descending.
SELECT Class, AVG(age) FROM captain GROUP BY Class ORDER BY Class DESC
SELECT "Class", AVG("age") FROM "captain" GROUP BY "Class" ORDER BY "Class" DESC