题解 | #某宝店铺折扣率#

select 
    round(sum(sales_price)/sum(amount)*100,2)
from (select 
    p.item_id,s.sales_price,
    s.sales_num*p.tag_price as amount
from product_tb p join sales_tb s 
on p.item_id = s.item_id) t

还行 不难