/*30. Write a query in SQL to return the reviewer name, movie title, and stars for those movies which reviewed by a reviewer
 and must be rated. Sort the result by reviewer name, movie title, and number of stars. */
    SELECT rev_name, mov_title, rev_stars   
     FROM reviewer, rating, movie   
      WHERE reviewer.rev_id=rating.rev_id   
       AND movie.mov_id=rating.mov_id   
         AND reviewer.rev_name IS NOT NULL   
           AND rating.rev_stars IS NOT NULL  
    ORDER BY rev_name, mov_title, rev_stars;  