Cumulative Sales By Product

You are working with the sales team of an e-commerce store to analyze their monthly performance.

They give you the sales table that tracks every purchase made on the store. The table contains the columns id (purchase id), product_id, date (purchase date), and price.

Write a SQL query to compute the cumulative sum of sales for each product, sorted by product_id and date.

Note: The cumulative sum for a product on a given date is the sum of the price of all purchases of the product that happened on that date and on all previous dates.

Example:

Input:

sales table

Output: