/* Задание 1 */

SELECT 
	u.id,
	u."name",
	o.id AS order_id,
	o.order_date,
	ROW_NUMBER() OVER (
		PARTITION BY u.id
		ORDER BY o.order_date) AS order_number_for_user
FROM 
	users u 
INNER JOIN
	orders o ON u.id = o.user_id

	
/* Задание 2 */
	
WITH order_revenue_cte AS (
	SELECT 
		oi.order_id,
		oi.quantity * oi.price_at_purchase AS order_revenue
	FROM 
		order_items oi
	)
SELECT 
	u.id,
	u."name",
	o.id AS order_id,
	o.order_date,
	orc.order_revenue,
	sum(orc.order_revenue) OVER (
		PARTITION BY u.id
		ORDER BY o.order_date 
		ROWS UNBOUNDED PRECEDING
	) AS running_revenue_for_user
FROM 
	users u 
INNER JOIN
	orders o ON u.id = o.user_id
INNER JOIN 
	order_revenue_cte orc ON o.id = orc.order_id
	

/* Задание 3 */
	
WITH user_revenue_cte AS (
	SELECT 
		o.user_id,
		oi.quantity * oi.price_at_purchase AS order_revenue,
		sum(oi.quantity * oi.price_at_purchase) OVER (
			PARTITION BY o.user_id) AS user_total_revenue
	FROM
		orders o
	INNER JOIN
		order_items oi ON o.id = oi.order_id)
SELECT DISTINCT
	u."name",
	urc.user_total_revenue,
	RANK() OVER (ORDER BY urc.user_total_revenue DESC) AS revenue_rank,
	DENSE_RANK() OVER (ORDER BY urc.user_total_revenue DESC) AS revenue_dense_rank
FROM 
	users u 
INNER JOIN 
	user_revenue_cte urc ON u.id = urc.user_id
	

/* Задание 4 */
	
SELECT 
	u.name AS user_name,
	o.id AS order_id,
	o.order_date,
	FIRST_VALUE(o.order_date) OVER (
		PARTITION BY o.user_id
		ORDER BY o.order_date
	) AS first_order_date,
	LAST_VALUE(o.order_date) OVER (
		PARTITION BY o.user_id
		ORDER BY o.order_date
		ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
	) AS last_order_date
FROM 
	users u 
INNER JOIN
	orders o ON u.id = o.user_id;
	

/* Задание 5 */

SELECT 
	u.name,
	o.id,
	count(o.id) OVER (
		PARTITION BY o.user_id) AS orders_per_user 
FROM
	users u 
INNER JOIN 
	orders o ON u.id = o.user_id 


/* Задание 6 */

WITH order_revenue_cte AS (
	SELECT 
		oi.order_id,
		oi.quantity * oi.price_at_purchase AS order_revenue
	FROM 
		order_items oi
	)
SELECT
	u.name,
	o.id,
	o.order_date,
	orc.order_revenue,
	lag(orc.order_revenue) OVER (
		PARTITION BY o.user_id
		ORDER BY o.order_date
	) AS prev_order_revenue
FROM
	users u 
INNER JOIN
	orders o ON u.id = o.user_id 
INNER JOIN 
	order_revenue_cte orc ON o.id = orc.order_id


/* Задание 7 */

WITH category_revenue_cte AS (
	SELECT
		p.category, 
		date_trunc('day', o.order_date)::date AS order_period,
		sum(oi.quantity * oi.price_at_purchase) AS daily_category_revenue
	FROM
		products p 
	LEFT JOIN
		order_items oi ON p.id = oi.product_id 
	INNER JOIN 
		orders o ON oi.order_id = o.id
	GROUP BY 1, 2)
SELECT 
	cr_cte.*,
	sum(cr_cte.daily_category_revenue) OVER (
		PARTITION BY cr_cte.category
		ORDER BY cr_cte.order_period
		ROWS UNBOUNDED PRECEDING
	) AS running_category_revenue
FROM 
	category_revenue_cte cr_cte;