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)

Visualize a bar chart showing the average age of captains in each class.
SELECT Class, AVG(age) FROM captain GROUP BY Class
SELECT "Class", AVG("age") FROM "captain" GROUP BY "Class"