CREATE TABLE roller_coaster (Roller_Coaster_ID INT, Name TEXT, Park TEXT, Country_ID INT, Length FLOAT, Height FLOAT, Speed TEXT, Opened TEXT, Status TEXT)
CREATE TABLE country (Country_ID INT, Name TEXT, Population INT, Area INT, Languages TEXT)

Show the names of countries and the average speed of roller coasters from each country Plot them as bar chart, sort from high to low by the Name please.
SELECT T1.Name, AVG(T2.Speed) FROM country AS T1 JOIN roller_coaster AS T2 ON T1.Country_ID = T2.Country_ID GROUP BY T1.Name ORDER BY T1.Name DESC
SELECT "T1"."Name", AVG("T2"."Speed") FROM "country" AS "T1" JOIN "roller_coaster" AS "T2" ON "T1"."Country_ID" = "T2"."Country_ID" GROUP BY "T1"."Name" ORDER BY "T1"."Name" DESC NULLS LAST