SELECT Latest 取得最近的信息

SELECT
    beyond_id,
    year_month,
    detail_info
FROM
    t_beyond b
INNER JOIN
(
    SELECT
        beyond_id,
        MAX(year_month) AS year_month
    FROM
        t_beyond
    WHERE
        year_month <= '20100912'
    GROUP BY
        beyond_id
) m
ON
    b.beyond_id = m.beyond_id
AND
    b.year_month = m.year_month