13、Obtain a list, in alphabetical order, of actors who've had at least 30 starring roles.
答案：
SELECT name FROM casting JOIN actor ON (actorid=actor.id) WHERE ord=1 GROUP BY name HAVING COUNT(*)>=30;
14、List the films released in the year 1978 ordered by the number of actors in the cast, then by title
答案：
SELECT title,COUNT(actorid) FROM casting JOIN actor ON (actor.id=casting.actorid) JOIN movie ON (movie.id=casting.movieid) WHERE yr='1978' GROUP BY title ORDER BY COUNT (actorid) DESC,title;
15、List all the people who have worked with 'Art Garfunkel'.
答案：
SELECT DISTINCT name FROM actor WHERE id IN (SELECT actorid FROM casting WHERE movieid IN
(SELECT movieid FROM casting WHERE actorid =
(SELECT id FROM actor WHERE name='Art Garfunkel')))
AND actor.name<>'Art Garfunkel';
