tricky questions to be solve

[ougesh]

Hi, am stuck on some question from : http://sqlzoo.net/3.htm
can anyone please help me to get the answer of section 4a,b,c,d and e.
please

[debasisdas]

Lets see what you have tried.

[ougesh]

4a.

SELECT COUNT(movie.id),movie.yr FROM movie
JOIN actor ON actor.id=movie.id
JOIN casting ON movie.id=casting.movieid
WHERE actor.name='John Travolta'

4b.

SELECT movie.title, actor.name FROM movie
JOIN casting ON movie.id=casting.movieid
JOIN actor ON actor.id=movie.id
WHERE movie.director='Julie Andrews' AND casting.ord=1

4c.
SELECT actor.name FROM actor
JOIN casting ON actor.id=casting.actorid
WHERE casting.ord>1

4d.

SELECT movie.title,casting.ord FROM movie
JOIN casting ON movie.id=casting.movieid
WHERE movie.yr=1978
ORDER BY casting.ord ASC

4e.

[ougesh]

thank you in advance for correcting my mistakes.
i think that i have wrongly understood the concepts of JOIN despite my several trials, can you please help