题解 | #某宝店铺折扣率#

# 步骤一：拉表格列出每一单的实际价格结算金额和标签价格结算金额
# select sales_price, pt.tag_price*st.sales_num as tag_sales_price
# from sales_tb as st
# left join product_tb as pt using(item_id)
# where st.sales_date like '2021-11%'

# 步骤二：合计步骤一表格的两列数据，计算统计折扣率
select round((sum(t1.sales_price) / sum(t1.tag_sales_price))*100, 2) as 'discount_rate(%)'
from (select sales_price, pt.tag_price*st.sales_num as tag_sales_price
from sales_tb as st
left join product_tb as pt using(item_id)
where st.sales_date like '2021-11%'
     ) as t1