取时间段内每类最新数据

SELECT
    TT1.STCD,
    TT1.STNM,
    TT1.LGTD,
    TT1.LTTD,
    TT2.Z,
    TT2.TM
FROM
    (
        SELECT
            T .STCD,
            T .STNM,
            T .LGTD,
            T .LTTD
        FROM
            ST_STBPRP_B T
        WHERE
            T .ADMAUTH != '气象'
        AND T .RVNM = '长江'
    ) TT1,
    (
        SELECT
            XX.STCD,
            XX.tm,
            XX.z
        FROM
            ST_RIVER_R XX,
            (
                SELECT
                    T .STCD,
                    "MAX" (T .TM) maxTM
                FROM
                    ST_RIVER_R T
                WHERE
                    T .TM < SYSDATE
                AND T .TM > (SYSDATE - 3 / 24)
                GROUP BY
                    T .STCD
            ) YY
        WHERE
            XX.STCD = YY.STCD
        AND XX.TM = YY.MAXTM
    ) TT2
WHERE
    TT1.STCD = TT2.STCD