题解 | 某宝店铺折扣率

with sum_sales as(
    select
        a.item_id item_id,
        max(tag_price)*sum(sales_num) sum_price,
        sum(sales_price) sales_price
    from product_tb a left join sales_tb b
        on a.item_id=b.item_id
    group by a.item_id
)

select 
    round(sum(sales_price)*100/sum(sum_price),2) discount_rate
from sum_sales