-- 1069. Product Sales Analysis II
--Table: Sales
--
--+-------------+-------+
--| Column Name | Type  |
--+-------------+-------+
--| sale_id     | int   |
--| product_id  | int   |
--| year        | int   |
--| quantity    | int   |
--| price       | int   |
--+-------------+-------+
--sale_id is the primary key of this table.
--product_id is a foreign key to Product table.
--Note that the price is per unit.
--Table: Product
--
--+--------------+---------+
--| Column Name  | Type    |
--+--------------+---------+
--| product_id   | int     |
--| product_name | varchar |
--+--------------+---------+
--product_id is the primary key of this table.
--
--
--Write an SQL query that reports the total quantity sold for every product id.
--
--The query result format is in the following example:
--
--Sales table:
--+---------+------------+------+----------+-------+
--| sale_id | product_id | year | quantity | price |
--+---------+------------+------+----------+-------+
--| 1       | 100        | 2008 | 10       | 5000  |
--| 2       | 100        | 2009 | 12       | 5000  |
--| 7       | 200        | 2011 | 15       | 9000  |
--+---------+------------+------+----------+-------+
--
--Product table:
--+------------+--------------+
--| product_id | product_name |
--+------------+--------------+
--| 100        | Nokia        |
--| 200        | Apple        |
--| 300        | Samsung      |
--+------------+--------------+
--
--Result table:
--+--------------+----------------+
--| product_id   | total_quantity |
--+--------------+----------------+
--| 100          | 22             |
--| 200          | 15             |
--+--------------+----------------+

SELECT product_id, SUM(quantity) AS total_quantity FROM Sales GROUP BY product_id;