select
    product_id,
    coalesce(round(sum(if_click)/count(if_click),3),0) ctr,
    coalesce(round(sum(if_cart)/sum(if_click),3)) cart_rate,
    coalesce(round(sum(if_payment)/sum(if_cart),3)) payment_rate,
    coalesce(round(sum(if_refund)/sum(if_payment),3)) refund_rate    
from tb_user_event
where date_format(event_time,'%Y-%m')='2021-10'
group by product_id
having sum(if_refund)/sum(if_payment)<=0.5
order by product_id