Completed Lab

Lab-sql-window-functions.sql

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+use sakila;
+-- Challenge 1: Using the SQL RANK() Function
+
+-- Step 1: Rank films by their length
+CREATE TEMPORARY TABLE ranked_films AS
+SELECT 
+    title,
+    length,
+    RANK() OVER (ORDER BY length DESC) AS 'rank'
+FROM 
+    film
+WHERE 
+    length IS NOT NULL AND length > 0;
+SELECT * FROM ranked_films;
+
+-- Step 2: Rank films by length within the rating category 
+CREATE TEMPORARY TABLE ranked_films_by_rating AS
+SELECT 
+    title,
+    length,
+    rating,
+    RANK() OVER (PARTITION BY rating ORDER BY length DESC) AS 'rank'
+FROM 
+    film
+WHERE 
+    length IS NOT NULL AND length > 0;
+
+SELECT * FROM ranked_films_by_rating;
+
+-- Step 3: Actor or actress who has acted in the greatest number of films
+CREATE TEMPORARY TABLE actor_film_count AS
+SELECT 
+    actor.actor_id,
+    actor.first_name,
+    actor.last_name,
+    COUNT(film_actor.film_id) AS film_count
+FROM 
+    actor
+JOIN 
+    film_actor ON actor.actor_id = film_actor.actor_id
+GROUP BY 
+    actor.actor_id, actor.first_name, actor.last_name;
+
+CREATE TEMPORARY TABLE max_actor_films AS
+SELECT 
+    film.film_id,
+    film.title,
+    actor_film_count.actor_id,
+    actor_film_count.first_name,
+    actor_film_count.last_name,
+    actor_film_count.film_count,
+    RANK() OVER (PARTITION BY film.film_id ORDER BY actor_film_count.film_count DESC) AS 'ranked'
+FROM 
+    film
+JOIN 
+    film_actor ON film.film_id = film_actor.film_id
+JOIN 
+    actor_film_count ON film_actor.actor_id = actor_film_count.actor_id;
+
+SELECT 
+    title,
+    first_name,
+    last_name,
+    film_count
+FROM 
+    max_actor_films
+WHERE 
+    ranked = 1;
+
+-- Challenge 2: Analyzing Customer Activity and Retention
+
+-- Step 1: Retrieve the number of monthly active customers
+CREATE TEMPORARY TABLE monthly_active AS
+SELECT 
+    DATE_FORMAT(rental_date, '%Y-%m') AS month,
+    COUNT(DISTINCT customer_id) AS active_customers
+FROM 
+    rental
+GROUP BY 
+    DATE_FORMAT(rental_date, '%Y-%m');
+
+SELECT * FROM monthly_active;
+
+-- Step 2: Retrieve the number of active users in the previous month
+CREATE TEMPORARY TABLE previous_month_active AS
+SELECT 
+    month,
+    active_customers,
+    LAG(active_customers, 1) OVER (ORDER BY month) AS previous_month_active_customers
+FROM 
+    monthly_active;
+
+SELECT * FROM previous_month_active;
+
+-- Step 3: Calculate the percentage change in the number of active customers
+CREATE TEMPORARY TABLE percentage_changes AS
+SELECT 
+    month,
+    active_customers,
+    previous_month_active_customers,
+    ((active_customers - previous_month_active_customers) / previous_month_active_customers) * 100 AS percentage_change
+FROM 
+    previous_month_active;
+
+SELECT * FROM percentage_changes;
+-- --------------------------------------------------------------
+-- Step 4: Calculate the number of retained customers every month
+CREATE TEMPORARY TABLE monthly_client AS
+SELECT 
+    DATE_FORMAT(rental_date, '%Y-%m') AS months,
+    customer_id
+FROM 
+    rental
+GROUP BY 
+    DATE_FORMAT(rental_date, '%Y-%m'), customer_id;
+
+
+CREATE TEMPORARY TABLE previous_month_client AS
+SELECT 
+    DATE_FORMAT(rental_date, '%Y-%m') AS months,
+    customer_id
+FROM 
+    rental
+GROUP BY 
+    DATE_FORMAT(rental_date, '%Y-%m'), customer_id;
+
+CREATE TEMPORARY TABLE retained_cust AS
+SELECT 
+    ma.months AS current_month,
+    COUNT(DISTINCT ma.customer_id) AS active_customers,
+    COUNT(DISTINCT pm.customer_id) AS retained_customers
+FROM 
+    monthly_client ma
+LEFT JOIN 
+    previous_month_client pm 
+ON 
+    ma.customer_id = pm.customer_id 
+    AND DATE_FORMAT(DATE_SUB(concat(ma.months,'-01'), INTERVAL 1 MONTH), '%Y-%m') = pm.months
+GROUP BY 
+    ma.months;
+
+SELECT * FROM retained_cust;