题目链接：​​点击打开链接​​

题目大意：略。

解题思路：略。

AC 代码

SELECT p.product_id, ROUND(SUM(price * units) / SUM(units), 2) average_price
FROM Prices p JOIN UnitsSold u ON p.product_id = u.product_id AND u.purchase_date BETWEEN start_date AND end_date
GROUP BY p.product_id