1070. Product Sales Analysis III

Table: Sales

(sale_id, year) is the primary key (combination of columns with unique values) of this table.
product_id is a foreign key (reference column) to Product table.
Each row of this table shows a sale on the product product_id in a certain year.
Note that the price is per unit.

Table: Product

product_id is the primary key (column with unique values) of this table.
Each row of this table indicates the product name of each product.

Write a solution to select the product id, year, quantity, and price for the first year of every product sold.

Return the resulting table in any order.

The result format is in the following example.

Example 1:

Input:
Sales table:

Product table:

Output:

這題描述不好，單純要達到範例要求只需要。

SELECT product_id , MIN(year) AS first_year ,quantity , price 
FROM Sales 
GROUP BY product_id

而且多給Product table也會造成誤導。

但要通過submit的測試要用子查詢

SELECT product_id, year AS first_year, quantity, price
FROM Sales
WHERE (product_id, year) in (
    SELECT product_id, MIN(year) 
    FROM Sales
    GROUP BY product_id
)