题解 | #某宝店铺折扣率#

with f as (select pt.tag_price   as tag_price
                , st.sales_price as sales_price
                , st.sales_num   as sales_num
           from product_tb pt
                    inner join sales_tb st using (item_id))
select round(sum((sales_price)) * 100 / sum(tag_price * sales_num), 2) as 'discount_rate(%)'
from f;