cs50x Ps7 Movies 10.sql

Question

On the Pset page it says that the solution must have 3392 rows. I wrote two different solutions, both accepted by check50, with different number of rows.

The first one gives 3389 lines:

SELECT DISTINCT name FROM people
JOIN directors ON directors.person_id = people.id
JOIN movies ON movies.id  = directors.movie_id
JOIN ratings ON ratings.movie_id = movies.id
WHERE ratings.rating >= 9.0;

The second one gives 3392 lines:

SELECT name FROM people WHERE id IN
(SELECT person_id FROM directors WHERE MOVIE_ID IN
(SELECT movie_id FROM ratings WHERE rating >= 9.0));

Any idea on why they are both accepted and why they give different results?

Answer 1

There might be directors with same name/different person_id, which the first one handles doesn't handle well.

But I don't know why CS50 accepts the first query. Maybe it's because for the purpose of the query is just to select names and namesake doesn't matter much.