with
    t1 as (
        select
            l.customer_id,
            pay_ability,
            overdue_days
        from
            loan_tb l
            left join customer_tb c on l.customer_id = c.customer_id
    )
select
    pay_ability,
    concat (
        round(
            (
                sum(
                    case
                        when overdue_days is not null then 1
                        else 0
                    end
                ) / count(customer_id)
            ) * 100,
            1
        ),
        '%'
    ) overdue_ratio
from
    t1
group by
    pay_ability
order by
    overdue_ratio desc