1251. Average Selling Price

https://leetcode.com/problems/average-selling-price

Description

Table: Prices

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| product\_id    | int     |
| start\_date    | date    |
| end\_date      | date    |
| price         | int     |
+---------------+---------+
(product\_id, start\_date, end\_date) is the primary key for this table.
Each row of this table indicates the price of the product\_id in the period from start\_date to end\_date.
For each product\_id there will be no two overlapping periods. That means there will be no two intersecting periods for the same product\_id.

Table: UnitsSold

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| product\_id    | int     |
| purchase\_date | date    |
| units         | int     |
+---------------+---------+
There is no primary key for this table, it may contain duplicates.
Each row of this table indicates the date, units and product\_id of each product sold. 

Write an SQL query to find the average selling price for each product.

average_priceshould be rounded to 2 decimal places.

The query result format is in the following example:

Prices table:
+------------+------------+------------+--------+
| product\_id | start\_date | end\_date   | price  |
+------------+------------+------------+--------+
| 1          | 2019-02-17 | 2019-02-28 | 5      |
| 1          | 2019-03-01 | 2019-03-22 | 20     |
| 2          | 2019-02-01 | 2019-02-20 | 15     |
| 2          | 2019-02-21 | 2019-03-31 | 30     |
+------------+------------+------------+--------+
 
UnitsSold table:
+------------+---------------+-------+
| product\_id | purchase\_date | units |
+------------+---------------+-------+
| 1          | 2019-02-25    | 100   |
| 1          | 2019-03-01    | 15    |
| 2          | 2019-02-10    | 200   |
| 2          | 2019-03-22    | 30    |
+------------+---------------+-------+

Result table:
+------------+---------------+
| product\_id | average\_price |
+------------+---------------+
| 1          | 6.96          |
| 2          | 16.96         |
+------------+---------------+
Average selling price = Total Price of Product / Number of products sold.
Average selling price for product 1 = ((100 * 5) + (15 * 20)) / 115 = 6.96
Average selling price for product 2 = ((200 * 15) + (30 * 30)) / 230 = 16.96

ac