SELECT a.product_id, 
	  if( show_cnt=0,0,round(sum(if_click)/show_cnt,3 )) as ctr,
	  if( sum(if_click)=0,0,round(sum(if_cart)/sum(if_click),3) )   as cart_rate,
	  if( sum(if_cart)=0,0,round(sum(if_payment)/sum(if_cart),3 ) ) as payment_rate,
	  if( sum(if_payment)=0,0,round(sum(if_refund)/sum(if_payment),3) ) as refund_rate
from tb_user_event tb 
JOIN 
	(select product_id,count(uid) show_cnt from tb_user_event 
     where date_format(event_time,"%Y-%m")='2021-10' 
     GROUP BY product_id 
     )a
on tb.product_id=a.product_id
where date_format(event_time,"%Y-%m")='2021-10'
GROUP BY a.product_id
having refund_rate<=0.5 
ORDER BY product_id asc;