[lab-sql-self-cross-join] João

Lab-Sql-Self-Cross-Join.sql

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+-- 1) Getting all pairs of actors that worked together
+select distinct a3.actor_id as actor_id_1, a3.first_name as first_name_1, a3.last_name as last_name_1, a4.actor_id as actor_id_2, a4.first_name as first_name_2, a4.last_name as last_name_2
+from sakila.film_actor a1
+inner join sakila.film_actor a2 on a1.film_id = a2.film_id
+left join sakila.actor a3 on a1.actor_id = a3.actor_id
+left join sakila.actor a4 on a2.actor_id = a4.actor_id
+where a1.actor_id < a2.actor_id
+order by a3.actor_id asc, a4.actor_id asc;
+
+-- 2) Get all pairs of customers that have rented the same film more than 3 times
+select customer1.first_name as first_name_1, customer1.last_name as last_name_1, customer2.first_name as first_name_2, customer2.last_name as last_name_2, count(*) as rentals_of_the_same_film
+from(
+	select distinct customer_id, film_id
+	from sakila.rental rental
+	left join sakila.inventory inventory on rental.inventory_id = inventory.inventory_id
+) sub1
+left join (
+	select distinct customer_id, film_id
+	from sakila.rental rental
+	left join sakila.inventory inventory on rental.inventory_id = inventory.inventory_id
+) sub2 on sub1.film_id = sub2.film_id
+left join sakila.customer customer1 on sub1.customer_id = customer1.customer_id
+left join sakila.customer customer2 on sub2.customer_id = customer2.customer_id
+where sub1.customer_id < sub2.customer_id
+group by customer1.first_name, customer1.last_name, customer2.first_name, customer2.last_name
+having count(*) > 3
+order by count(*) desc;
+
+-- 3) Getting all possible pairs of actors and films
+select distinct film.title, actor_name.first_name as actor_first_name, actor_name.last_name as actor_last_name
+from sakila.film_actor actor
+cross join sakila.film film
+left join sakila.actor actor_name on actor.actor_id = actor_name.actor_id;