题解 | 查询出不同类别商品中，销售金额排名前三且利润率超过 20%的商品信息

select
    product_id,
    product_name,
    category_id,
    sales_amount,
    profit_rate
from (
    select
        p.product_id,
        product_name,
        category_id,
        sales_amount,
        rank() over(partition by category_id order by sales_amount desc) rk,
        round((sales_amount-cost_amount)/sales_amount, 2) profit_rate
    from
        product_category p
    left join sales_and_profit s on p.product_id=s.product_id
    order by category_id, sales_amount desc, p.product_id
) sub
where rk <= 3 and profit_rate > 0.2