sql_practice.sql

SELECT
	(SELECT COUNT(*) FROM film) AS films,
	(SELECT COUNT(*) FROM actor) AS actors
;

SELECT COUNT(*)
FROM address
WHERE postal_code IS NULL;

SELECT first_name
FROM actor
WHERE first_name LIKE 'P%';

SELECT COUNT(*)
FROM actor
WHERE first_name LIKE 'P%' OR  first_name LIKE 'A%';

SELECT first_name,
	last_name,
	COUNT(*) AS count_no
FROM actor 
INNER JOIN film_actor
ON actor.actor_id = film_actor.actor_id
GROUP BY 1, 2
ORDER BY count_no DESC 
LIMIT 10;

SELECT DISTINCT rating FROM film;

WITH t AS(
	SELECT rating, 
		COUNT(*) AS count_rating,
		(SELECT COUNT(*) FROM film) AS total
	FROM film
	GROUP BY rating
)

SELECT rating, 
	count_rating,
	count_rating/ CAST(total AS REAL) AS ratingPercentage
FROM t ; 

SELECT 
	rating,
	COUNT(*) AS Total_count
FROM film
GROUP BY 1;

SELECT
	rating,
	total_rating,
	total_rating/CAST(total_count AS REAL) AS ratingPercent
FROM(
	SELECT 
		rating,
		COUNT(*) AS total_rating,
		(SELECT COUNT(*) FROM film) AS total_count
	FROM film
GROUP BY rating
)
ORDER BY total_rating DESC;