select
if(pay_method = '','error', pay_method) pay_method,
num
from
(
    select
    pay_method
    ,count(*) num
    from user_client_log u
    join product_info p
    on u.product_id = p.product_id
    where p.product_name = 'anta' and step = 'select'
    group by pay_method
    ) t
order by num desc