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

For each type, what is the average tonnage, and show X in desc order.
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