with
t1 as(
    select
        pay_method,
        count(pay_method) as cnt
    from
        user_client_log left join product_info using(product_id)
    where
        product_name='anta' and step='select'
    group by
        pay_method
),
t2 as(
    select
        (
            case
                when pay_method='' then 'error'
                else pay_method
            end
        ) as pay_method,
        cnt
    from
        t1
)

select * from t2