NO JOINS -> filter with DENSE_RANK() 
Intuitionthe clue was "for the first year of every product sold."Approachrank them by YEAR (ORDER BY year) and split them on product_id (PARTITION BY product_id
# Intuition
<!-- Describe your first thoughts on how to solve this problem. -->
the clue was ***"for the first year of every product sold."***

# Approach
<!-- Describe your approach to solving the problem. -->
rank them by YEAR (ORDER BY year) and split them on product_id (PARTITION BY product_id)

# Code
```mysql []
SELECT product_id, year AS first_year, quantity, price
FROM (
  SELECT product_id, year, quantity, price,
         DENSE_RANK() OVER (PARTITION BY product_id ORDER BY year) AS rn
  FROM Sales
) AS s
WHERE rn = 1;
```
['Database', 'MySQL']