refactor 1384

Author: fishercoder1534

database/_1384.sql

@@ -1,72 +1,3 @@
---1384. Total Sales Amount by Year
---
---Table: Product
---
---+---------------+---------+
---| Column Name   | Type    |
---+---------------+---------+
---| product_id    | int     |
---| product_name  | varchar |
---+---------------+---------+
---product_id is the primary key for this table.
---product_name is the name of the product.
---
---
---Table: Sales
---
---+---------------------+---------+
---| Column Name         | Type    |
---+---------------------+---------+
---| product_id          | int     |
---| period_start        | varchar |
---| period_end          | date    |
---| average_daily_sales | int     |
---+---------------------+---------+
---product_id is the primary key for this table.
---period_start and period_end indicates the start and end date for sales period, both dates are inclusive.
---The average_daily_sales column holds the average daily sales amount of the items for the period.
---
---Write an SQL query to report the Total sales amount of each item for each year, with corresponding product name, product_id, product_name and report_year.
---
---Dates of the sales years are between 2018 to 2020. Return the result table ordered by product_id and report_year.
---
---The query result format is in the following example:
---
---
---Product table:
---+------------+--------------+
---| product_id | product_name |
---+------------+--------------+
---| 1          | LC Phone     |
---| 2          | LC T-Shirt   |
---| 3          | LC Keychain  |
---+------------+--------------+
---
---Sales table:
---+------------+--------------+-------------+---------------------+
---| product_id | period_start | period_end  | average_daily_sales |
---+------------+--------------+-------------+---------------------+
---| 1          | 2019-01-25   | 2019-02-28  | 100                 |
---| 2          | 2018-12-01   | 2020-01-01  | 10                  |
---| 3          | 2019-12-01   | 2020-01-31  | 1                   |
---+------------+--------------+-------------+---------------------+
---
---Result table:
---+------------+--------------+-------------+--------------+
---| product_id | product_name | report_year | total_amount |
---+------------+--------------+-------------+--------------+
---| 1          | LC Phone     |    2019     | 3500         |
---| 2          | LC T-Shirt   |    2018     | 310          |
---| 2          | LC T-Shirt   |    2019     | 3650         |
---| 2          | LC T-Shirt   |    2020     | 10           |
---| 3          | LC Keychain  |    2019     | 31           |
---| 3          | LC Keychain  |    2020     | 31           |
---+------------+--------------+-------------+--------------+
---LC Phone was sold for the period of 2019-01-25 to 2019-02-28, and there are 35 days for this period. Total amount 35*100 = 3500.
---LC T-shirt was sold for the period of 2018-12-01 to 2020-01-01, and there are 31, 365, 1 days for years 2018, 2019 and 2020 respectively.
---LC Keychain was sold for the period of 2019-12-01 to 2020-01-31, and there are 31, 31 days for years 2019 and 2020 respectively.
---
-
 /* Write your T-SQL query statement below */
 --credit: https://leetcode.com/problems/total-sales-amount-by-year/discuss/544812/Using-Recursive-CTE-to-get-all-the-possible-dates