select 
    p.name as product_name, 
    sum(o.quantity) as total_sales,
    row_number() over(partition by p.category order by sum(quantity) desc) as category_rank
from orders as o 
    join products as p on o.product_id = p.product_id
group by o.product_id, p.category
order by p.category asc, total_sales desc, o.product_id asc

第5行，quantity改成o.quantity就会报错，不知道咋回事