diff --git a/README.md b/README.md
index 608c120..19a0904 100644
--- a/README.md
+++ b/README.md
@@ -161,14 +161,17 @@ ORDER BY rating DESC
 
 [1251. Average Selling Price](https://leetcode.com/problems/average-selling-price/)
 ```sql
--- avg(selling), round 2
 SELECT p.product_id, 
-  ROUND(SUM(price * units) / SUM(units), 2) AS average_price
+  ROUND(
+      IFNULL(SUM(price * units) / SUM(units), 0),
+      2
+  ) AS average_price
 FROM Prices p
 LEFT JOIN UnitsSold s
 ON p.product_id = s.product_id
 AND purchase_date BETWEEN start_date AND end_date
-GROUP BY p.product_id
+GROUP BY p.product_id;
+
 ```
 
 [1075. Project Employees I](https://leetcode.com/problems/project-employees-i)