CREATE TABLE Rating (rID NUMBER, mID NUMBER, stars NUMBER, ratingDate DATE)
CREATE TABLE Reviewer (rID NUMBER, name CLOB)
CREATE TABLE Movie (mID NUMBER, title CLOB, year NUMBER, director CLOB)

For each director, return the director's name together with the highest rating among all of their movies and ignore movies whose director is NULL. Could you plot the result with a pie chart?
SELECT director, MAX(T1.stars) FROM Rating AS T1 JOIN Movie AS T2 ON T1.mID = T2.mID WHERE director <> "null" GROUP BY director
SELECT "director", MAX("T1"."stars") FROM "Rating" "T1" JOIN "Movie" "T2" ON "T1"."mID" = "T2"."mID" WHERE "director" <> "null" GROUP BY "director"