Sql server 获取给定日期的信息/距离给定日期最近的日期

我正在尝试查找ID的状态是否为活动/在给定日期备份/距离给定日期最近的日期

我的CTE中的数据：

ID      StatusDate              Status  Order
2145    2012-04-29              n/a     1
2145    2012-08-02              Backup  2
2145    2012-09-27              Backup  3
2145    2012-11-07              Backup  4
2145    2012-11-09              Active  5
2145    2012-11-12              Backup  6
2145    2012-12-13              Pending 7
2145    2012-12-18              Sold    8
2146    2012-10-15              Pending 1
2146    2012-10-15              n/a     2
2146    2012-12-19              Sold    3
4145    2012-04-24              Active  1
4145    2012-04-24              Active  2
4145    2012-05-22              Pending 3
4145    2012-09-13              Active  4
4145    2012-09-13              Active  5
4145    2012-12-05              Pending 6
4145    2012-12-19              Sold    7
7175    2012-11-08              n/a     1
7175    2012-12-01              Backup  2
7175    2012-12-05              Active  3
7175    2012-12-06              Pending 4
7175    2012-12-19              Sold    5

结果:

Analysis         09/20/2012   12/19/2012  3/20/2013

Total Active         2          0           0

结果的标题应为：自当前日期起6个月前的日期、自当前日期起3个月前的日期和当前日期**

以下是我正在努力解决的问题：

 ;WITH x AS 
    (
        SELECT  ID,statusdate,status , row_number() over (partition by ID order by statusdate DESC )  as RN1
        FROM 
            (SELECT ID,statusdate,status,
                   rn = row_number() over (partition by ID order by statusdate ) 
            FROM tblHistory   (nolock)
             WHERE [statusdate] <=  '20120920' AND
             ID in ('2145','2146','4145''7175')
            )  AS A
     )

SELECT  ID,statusdate,status 
FROM x 
WHERE rn1 = 1 AND status IN ('Backup','Active')