select style_id, 
round(sum(sales_num)/(max(a)-sum(sales_num))*100,2), 
round(sum(sales_price)/max(b)*100,2)
from sales_tb left join 
  (select *, 
    sum(inventory)over(partition by style_id) a,
    sum(tag_price*inventory)over(partition by style_id) b
  from product_tb) as tb1
using(item_id)
group by style_id
order by style_id

#思路：
#①在表连接之前，把每种style的备货数量、备货金额用窗口函数算出来；
#②表连接，根据style_id分组，计算即可。