WindowFuncs Homework done

aharlamcev/postgresql/WindowFunctionHomework.sql

@@ -22,21 +22,51 @@ values (1, 'iPhone 14', 'smartphone', 799, true, 'iphone@apple.com'),
 alter table products_extended
 alter column price type DECIMAL(10, 2)
 
-select * from products_extended
-
+------------------ Задание №1  (По нему ты говорил, что нечитаемо, объясни как переделать pls <3)
 with email_false as (select * from 
 (
-select category, name, price, email_support, row_number() over (partition by category order by price desc) as rn
-from products_extended where email_support is null) where rn = 1
+select category, name, price, email_support, 
+row_number() over (partition by category order by price desc) as rn
+from products_extended 
+where email_support is null) 
+where rn = 1
 ),
 
 email_true as (select * from 
 (
-select category, name, price, email_support, row_number() over (partition by category order by price desc) as rn
-from products_extended where email_support is not null) where rn = 1
+select category, name, price, email_support, 
+row_number() over (partition by category order by price desc) as rn
+from products_extended 
+where email_support is not null) 
+where rn = 1
 )
 
 select category, name, price, email_support from email_false
 union all
 select category, name, price, email_support from email_true
 order by category, price desc
+
+---------------------- Задание №2 (Переделал с двух оконок в одном запросе на СТЕ с одной оконкой внутри)
+with get_data as (
+select name, category, price,
+LEAD(price) OVER (PARTITION BY category order by price) AS next_price
+from products_extended
+)
+
+select name, category, price, next_price,
+price - next_price AS diff
+from get_data
+
+--------------------- Задание №3
+select category, name, price,
+SUM(price) over (partition by category order by price) as cumulative_sales
+from products_extended
+
+---------------------- Задание №4
+with get_data as (
+select category, name, price, AVG(price) over (partition by category) as avg_price
+from products_extended
+)
+select category, name, price, avg_price, 
+case when price > avg_price then 'true' else 'false' end as is_above_avg
+from get_data