Identify favorite actors of customer groups

Data-Driven Decision Making in SQL

Irene Ortner

Data Scientist at Applied Statistics

Combining SQL statements in one query

LEFT JOIN
WHERE
GROUP BY
HAVING
ORDER BY

From renting records to customer and actor information

Our question: Who is the favorite actor for a certain customer group?

Join table renting with tables

customers
actsin
actors

SELECT *
FROM renting as r
LEFT JOIN customers AS c
ON r.customer_id = c.customer_id
LEFT JOIN actsin as ai
ON r.movie_id = ai.movie_id
LEFT JOIN actors as a
ON ai.actor_id = a.actor_id;

Male customers

Actors which play most often in movies watched by male customers.

SELECT a.name, 
       COUNT(*)
FROM renting as r
LEFT JOIN customers AS c
ON r.customer_id = c.customer_id
LEFT JOIN actsin as ai
ON r.movie_id = ai.movie_id
LEFT JOIN actors as a
ON ai.actor_id = a.actor_id

WHERE c.gender = 'male'
GROUP BY a.name;

Who is the favorite actor?

Actor being watched most often.
Best average rating when being watched.

SELECT a.name, 
       COUNT(*) AS number_views, 
       AVG(r.rating) AS avg_rating
FROM renting as r
LEFT JOIN customers AS c
ON r.customer_id = c.customer_id
LEFT JOIN actsin as ai
ON r.movie_id = ai.movie_id
LEFT JOIN actors as a
ON ai.actor_id = a.actor_id

WHERE c.gender = 'male'
GROUP BY a.name;

Add HAVING and ORDER BY

SELECT a.name, 
       COUNT(*) AS number_views, 
       AVG(r.rating) AS avg_rating
FROM renting as r
LEFT JOIN customers AS c
ON r.customer_id = c.customer_id
LEFT JOIN actsin as ai
ON r.movie_id = ai.movie_id
LEFT JOIN actors as a
ON ai.actor_id = a.actor_id

WHERE c.gender = 'male'
GROUP BY a.name
HAVING AVG(r.rating) IS NOT NULL
ORDER BY avg_rating DESC, number_views DESC;

Add HAVING and ORDER BY

| name               | number_views | avg_rating |
|--------------------|--------------|------------|
| Ray Romano         | 3            | 10.00      |
| Sean Bean          | 2            | 10.00      |
| Leonardo DiCaprio  | 3            | 9.33       |
| Christoph Waltz    | 3            | 9.33       |

Let's practice!

Data-Driven Decision Making in SQL