CREATE TABLE ship (ship_id NUMBER, name CLOB, type CLOB, built_year NUMBER, class CLOB, flag CLOB)
CREATE TABLE captain (captain_id NUMBER, name CLOB, ship_id NUMBER, age CLOB, class CLOB, rank CLOB)

What are the average and minimum age of captains in different class?
SELECT AVG(age), MIN(age), class FROM captain GROUP BY class
SELECT AVG("age"), MIN("age"), "class" FROM "captain" GROUP BY "class"