What is the average price of the products for each category?
SELECT avg(product_price) ,  product_category_code FROM products GROUP BY product_category_code
SELECT avg(product_price) ,  product_category_code FROM products GROUP BY product_category_code
[{'avg(product_price)': 35.0, 'product_category_code': 'Book'}, {'avg(product_price)': 2.88, 'product_category_code': 'Food'}, {'avg(product_price)': 66.67, 'product_category_code': 'Hardware'}]