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Lab_sql_joins.sql

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+USE sakila;
+-- Write SQL queries to perform the following tasks using the Sakila database:
+-- List the number of films per category.
+SELECT COUNT(sfc.film_id), sc.name as category
+FROM sakila.film_category as sfc
+LEFT JOIN sakila.category as sc
+ON sfc.category_id = sc.category_id
+GROUP BY category;
+
+-- Retrieve the store ID, city, and country for each store.
+SELECT ss.store_id AS store_id,  -- selecciono las columnas que quiero de las dos uniones realizadas (8)
+		sci.city as city,             
+		scou.country as country             
+FROM sakila.store as ss  -- mi primera tabla a unir (1)
+join sakila.address as sa -- mi segunda tabla a unir (2)
+on ss.address_id = sa.address_id -- columna comun de la primera unión (3)
+join sakila.city as sci -- mi tercera tabla unir con el resultado de la unión previa (4)
+on  sa.city_id = sci.city_id -- columna comun de la segunda unión (5)
+join sakila.country as scou -- mi cuarta tabla unir con el resultado de la unión previa (6)
+on  sci.country_id = scou.country_id; -- columna comun de la segunda unión (7)
+
+-- Calculate the total revenue generated by each store in dollars.
+SELECT ss.store_id AS store_id,  -- selecciono las columnas que quiero de las dos uniones realizadas (6)
+		SUM(sp.amount) as revenue            
+FROM sakila.store as ss  -- mi primera tabla a unir (1)
+join sakila.staff as st -- mi segunda tabla a unir (2)
+on ss.store_id = st.store_id -- columna comun de la primera unión (3)
+join sakila.payment as sp -- mi tercera tabla unir con el resultado de la unión previa (4)
+on  st.staff_id = sp.staff_id -- columna comun de la segunda unión (5)
+GROUP BY store_id;
+
+-- Determine the average running time of films for each category.
+SELECT sc.name as category_name, 
+		AVG(sf.length) as duration_mean
+FROM sakila.film as sf
+JOIN sakila.film_category as sfc
+on sf.film_id=sfc.film_id
+join sakila.category as sc
+on sfc.category_id=sc.category_id
+GROUP BY category_name;
+
+