CREATE TABLE mission (Mission_ID INT, Ship_ID INT, Code TEXT, Launched_Year INT, Location TEXT, Speed_knots INT, Fate TEXT)
CREATE TABLE ship (Ship_ID INT, Name TEXT, Type TEXT, Nationality TEXT, Tonnage INT)

Show different types of ships and the average tonnage of ships of each type in a bar chart, rank total number in descending order please.
SELECT Type, AVG(Tonnage) FROM ship GROUP BY Type ORDER BY AVG(Tonnage) DESC
SELECT "Type", AVG("Tonnage") FROM "ship" GROUP BY "Type" ORDER BY AVG("Tonnage") DESC NULLS LAST