lab done

lab sql joins.sql

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+-- 1
+select b.name as category, count(*) as number_of_films
+from film_category as a
+inner join category as b
+on a.category_id = b.category_id
+group by b.name;
+
+-- 2
+select a.store_id, b.address, c.city, d.country
+from store a
+inner join address b 
+on a.address_id = b.address_id
+inner join city c
+on b.city_id = c.city_id
+inner join country d
+on c.country_id = d.country_id;
+-- 3
+select sum(a.amount), b.store_id
+from payment a
+join staff b
+on a.staff_id = b.staff_id
+group by b.store_id;
+-- 4
+SELECT b.name as category, COUNT(a.film_id) AS number_of_films, round(AVG(c.length)) AS average_length
+FROM film_category AS a
+INNER JOIN category AS b
+    ON a.category_id = b.category_id
+INNER JOIN film AS c
+    ON a.film_id = c.film_id
+GROUP BY b.name;
+-- 5
+SELECT b.name as category, COUNT(a.film_id) AS number_of_films, round(AVG(c.length)) AS average_length
+FROM film_category AS a
+INNER JOIN category AS b
+    ON a.category_id = b.category_id
+INNER JOIN film AS c
+    ON a.film_id = c.film_id
+GROUP BY b.name
+ORDER BY average_length DESC;