window functions solve

2026-01-15 19:20:41 +03:00
parent f799062f35
commit 0dca45f922
3 changed files with 80 additions and 0 deletions
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 /*
 Задача 1:
 Для каждой категории показать 2 строки:
 - Самый дорогой товар с email'ом
 - Самый дорогой товар без email'а
 */
 with with_mail as (
 select category, name, price, email_support
 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
 ) t
 where rn = 1
 ),
 without_mail as (
 select category, name, price, email_support
 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
 ) t
 where rn = 1 
 )
 select * from with_mail
 union all
 select * from without_mail
 order by category;
 /*
 Задача 2:
 Для каждого товара показать:
 - `name` — название товара
 - `category` — категория товара
 - `price` — цена текущего товара
 - `next_price` — цена следующего товара внутри той же категории, упорядоченного по цене
 - `diff` — разница между ценой текущего товара и ценой следующего товара 
 (`price - next_price`)
 */
 select name, category, price, lead(price) over(partition by category order by price) as next_price, 
 price - lead(price) over(partition by category order by price) as diff
 from products_extended;
 /*
 Задача 3:
 Показать `category`, `name`, `price`, `cumulative_sales`
 Где `cumulative_sales` — это сумма `price` **внутри категории** по мере возрастания цены
 */
 select category, name, price, 
 sum(price) over (partition by category order by price) as cumulative_sales
 from products_extended;
 /*
 Задача 4:
 Вывести `category`, `name`, `price`, `avg_price`, `is_above_avg`
 Где `avg_price` — средняя цена по категории
 `is_above_avg = true`, если `price > avg_price`
 */
 select  category, name, price, 
 round(avg(price) over (partition by category), 1) as avg_price,
 price > avg(price) over (partition by category) as is_above_avg
 from products_extended;