select
    order_id,
    customer_name,
    order_date
from
    (
        select
            order_id,
            customer_name,
            order_date,
            row_number() over (
                partition by
                    customer_id
                order by
                    order_date desc
            ) rk
        from
            orders o
            join customers c using (customer_id)
    ) aa
where
    rk = 1;