题解 | 查询订单

select
    order_id,
    customer_name,
    order_date
from
    (
        select
            a.order_id,
            a.order_date,
            b.customer_name,
            row_number() over (
                partition by
                    a.customer_id
                order by
                    order_date desc
            ) as num
        from
            orders a,
            customers b
        where
            a.customer_id = b.customer_id
    ) c
where
    num = 1
order by
    customer_name