题解 | 店铺901国庆期间的7日动销率和滞销率

select dt,round(num1/num2,3) sale_rate,round((num2-num1)/num2,3) unsale_rate
from(
select distinct date(event_time) dt,
(select count(distinct tod.product_id) 
from tb_order_detail tod
join tb_order_overall too on tod.order_id = too.order_id
join tb_product_info tpi on tpi.product_id = tod.product_id
where shop_id = '901'
and timestampdiff(day,event_time,t2.event_time) between 0 and 6) num1,  //我就想不明白为啥这里日期比较必须引用t2.date而不能用dt别名呢？？？？？？？？
(select count(product_id)
from tb_product_info
where shop_id = '901'
) num2
from tb_order_overall t2
where date(event_time) between '2021-10-01' and '2021-10-03') as t1

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