Identificați actorii preferați ai grupurilor de clienți

Luarea Deciziilor Bazate pe Date în SQL

Irene Ortner

Data Scientist at Applied Statistics

Combinarea instrucțiunilor SQL într-o singură interogare

LEFT JOIN
WHERE
GROUP BY
HAVING
ORDER BY

De la înregistrări de închiriere la informații despre clienți și actori

Întrebarea noastră: Cine este actorul preferat al unui anumit grup de clienți?

Joinați tabela renting cu tabelele

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;

Clienți de sex masculin

Actorii care apar cel mai des în filmele vizionate de clienții de sex masculin.

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;

Cine este actorul preferat?

Actorul vizionat cel mai frecvent.
Cel mai bun rating mediu la vizionare.

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;

Adăugați HAVING și 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;

Adăugați HAVING și 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       |

Să exersăm!

Luarea Deciziilor Bazate pe Date în SQL