Merge pull request 'feat (sql): complete JOIN homework' (#93) from OS-412 into main

Reviewed-on: https://gitea.de-infra.servehttp.com/de-infrastructure/DWH/pulls/93
Reviewed-by: aleksey bogatyrev <abogatyrev@example.com>

pmikhailov/postgresql/.project

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>postgresql</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+	</buildSpec>
+	<natures>
+	</natures>
+</projectDescription>

pmikhailov/postgresql/joins.sql

@@ -0,0 +1,158 @@
+/* Задача 1
+ * Джойним в таком порядке т.к. не каждый юзер делал заказ
+ * + судя по порядку колонок мы хотим анализировать заказы
+ * (по сути выглядит так же как INNER)
+ * Но в обратном порядке можем увидеть кто не делал заказ
+ * и добавить их в условную рассылку
+ */
+SELECT 
+	o.id AS order_id, 
+	o.order_date, 
+	status, 
+	u."name" AS user_name, 
+	country
+FROM 
+	orders o
+LEFT JOIN 
+	users u ON o.user_id = u.id 
+	
+
+/* Задача 2 */
+	
+SELECT 
+	order_id, 
+	p."name" AS product_name, 
+	quantity, 
+	price_at_purchase
+FROM 
+	order_items oi
+LEFT JOIN 
+	products p ON oi.product_id = p.id  -- AND oi.order_id = 1 из правой таблицы будут NULL там, где оба условия не выполнены 
+WHERE order_id = 1 -- в задании другой номер - 101, надо исправить в Notion, данные на п.4 уже другие
+
+
+/* Задача 3 */
+
+SELECT 
+	order_id, 
+	u."name" AS user_name,
+	p."name" AS product_name, 
+	quantity, 
+	price_at_purchase
+FROM
+	orders o 
+LEFT JOIN 
+	order_items oi ON o.id =  oi.order_id 
+INNER JOIN 
+	users u ON o.user_id = u.id
+INNER JOIN
+	products p ON oi.product_id = p.id;
+
+
+/* Задача 4 */
+
+SELECT 
+	u."name" AS user_name,
+	o.id AS order_id,
+	status
+FROM 
+	users u 
+LEFT JOIN
+	orders o ON u.id = o.user_id 
+
+
+/* Задача 5 */
+
+SELECT
+	o.user_id,
+	u."name" AS user_name
+FROM
+	users u 
+LEFT JOIN
+	orders o ON u.id = o.user_id
+WHERE o.user_id IS NOT NULL
+
+
+/* Задача 6 */
+
+SELECT 
+	o.id AS order_id,
+	u.name AS user_name,
+	p.name AS product_name,
+	quantity
+FROM
+	orders o
+LEFT JOIN
+	order_items oi ON o.id = oi.order_id 
+INNER JOIN 
+	products p ON oi.product_id = p.id 
+INNER JOIN 
+	users u ON o.user_id = u.id
+WHERE p."name" ILIKE '%Mi Band 7%';
+
+
+/* Задача 7 */
+
+SELECT 
+	p.name AS product_name,
+	order_id,
+	quantity
+FROM 
+	products p 
+FULL JOIN 
+	order_items oi ON p.id = oi.product_id
+ORDER BY product_name;
+
+
+/* Задача 8 */
+
+SELECT 
+	o.id,
+	u."name" AS user_name,
+	p."name" AS product_name,
+	quantity,
+	price_at_purchase 
+FROM 
+	orders o 
+LEFT JOIN 
+	order_items oi ON o.id = oi.order_id 
+INNER JOIN 
+	users u ON o.user_id = u.id 
+LEFT JOIN
+	products p ON oi.product_id = p.id 
+WHERE 
+	o.status = 'paid';
+
+
+/* Задача 9 */
+
+SELECT 
+	o.id AS order_id,
+	o.order_date,
+	p."name" AS product_name,
+	quantity,
+	price_at_purchase
+FROM
+	orders o
+LEFT JOIN 
+	order_items oi ON o.id = oi.order_id
+INNER JOIN 
+	products p ON oi.product_id = p.id 
+INNER JOIN 
+	users u ON o.user_id = u.id
+WHERE u."name" ILIKE '%alice%';
+
+
+/* Задача 10 
+* Задача противоречит изначальным органичениям NOT NULL
+*/
+
+SELECT 
+	o.id AS order_id,
+	user_id,
+	status
+FROM
+	orders o 
+FULL JOIN
+	order_items oi ON oi.order_id = o.id 
+WHERE product_id IS NULL AND o.status = 'created';