SQL分组排序去重复的小实例

代码如下：

SELECT
    *
FROM
    (
        SELECT
            userid,
            classid,
            remark,
            ROW_NUMBER () OVER (
                PARTITION BY userid,
                classid
            ORDER BY
                addtime DESC
            ) AS row_bank
        FROM
            Eng24VIPCourseIntention
    ) AS ta
WHERE
    row_bank = 1

==========================
 PARTITIONBYuserid,classid 这里是按什么分组， 注意一下。