SQL) partition by

-- 고객별로 마지막 주문만 조회하기
select * from t_ord t1;

SELECT
    t2.*
FROM
    (
        SELECT
            t1.*,
            ROW_NUMBER()
            OVER(PARTITION BY t1.cus_id
                 ORDER BY
                     t1.ord_dt DESC, t1.ord_seq DESC
            ) ord_rnk
        FROM
            t_ord t1
    ) t2
WHERE
    t2.ord_rnk = 1;