Update ch03: 复杂一点的查询.md

ch03: 复杂一点的查询.md

@@ -333,9 +333,9 @@ SELECT product_id, product_name, sale_price
 我们再来看一下这个需求`选取出各商品种类中高于该商品种类的平均销售单价的商品`。SQL语句如下：
 ```sql
 SELECT product_type, product_name, sale_price
-  FROM product ASp1
+  FROM product AS p1
  WHERE sale_price > (SELECT AVG(sale_price)
-   FROM product ASp2
+   FROM product AS p2
                       WHERE p1.product_type =p2.product_type
    GROUP BY product_type);
 ```