CREATE TABLE phone (Name TEXT, Phone_ID INT, Memory_in_G INT, Carrier TEXT, Price FLOAT)
CREATE TABLE market (Market_ID INT, District TEXT, Num_of_employees INT, Num_of_shops FLOAT, Ranking INT)
CREATE TABLE phone_market (Market_ID INT, Phone_ID TEXT, Num_of_stock INT)

Bar graph to show mean memory in g from different carrier, sort X-axis from high to low order please.
SELECT Carrier, AVG(Memory_in_G) FROM phone GROUP BY Carrier ORDER BY Carrier DESC
SELECT "Carrier", AVG("Memory_in_G") FROM "phone" GROUP BY "Carrier" ORDER BY "Carrier" DESC NULLS LAST