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

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"