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)

Give me a bar chart for mean tonnage of each type, show by the bar in desc.
SELECT Type, AVG(Tonnage) FROM ship GROUP BY Type ORDER BY Type DESC
SELECT "Type", AVG("Tonnage") FROM "ship" GROUP BY "Type" ORDER BY "Type" DESC NULLS LAST