row_number() OVER(

SELECT
    cjdjh,
    id,
    f.valid_date,
    row_number() OVER(
        PARTITION BY cjdjh
    ORDER BY
        valid_date
    )
FROM

    p_work_cert f;

SELECT
    cjdjh AS cjdjh,
    note,
    rid,
    forecast_expire AS mindate
FROM
    (
        SELECT
            cjdjh AS cjdjh,
            note,
            rid,
            forecast_expire,
            expire_type,
            row_number() OVER(
                PARTITION BY cjdjh
            ORDER BY
                forecast_expire
            ) AS orwnum
        FROM
            view_forecast_all
    )
WHERE
    orwnum = 1

再套一层，起别名