sql server 2012上的超前和滞后功能

Question

我通过以下查询获得了以下数据

Select *
FROM        
    (Select RP.ins_user_id, RP.Loadno, Max(RP.trndte) 'M1', Min(RP.trndte)'M2', sum(RP.trnqty) 'QTY'
                 from
                    (select R.ins_user_id,R.trnqty, R.trndte,
                        "Loadno" =
                            case when
                            R.actcod = 'sstg' then R.lodnum 
                            else R.to_lodnum
                        end
            from dbo.RP_DlyTrn R
            where R.oprcod IN ('LPCK', 'RLPCK') 
            and R.actcod in ('caspck', 'otrpck', 'palpck', 'pcepck','sstg', 'list-start')
            and R.ship_id <> 0
            and R.trndte between '08/18/2014 17:25:00' and '08/19/2014 8:00:00') RP
            where RP.Loadno is not null
            group by RP.ins_user_id, RP.Loadno) rp2
            order by RP2.ins_user_id, RP2.Loadno

结果：

ins_user_id  Loadno            end time(M1)       start time(M2)        qty   start_time suc load  
AMCPHEE   L00000971730  2014-08-19 07:59:30   2014-08-19 07:47:16   7           Null
CBOWLEG   L00000968872  2014-08-18 18:35:37   2014-08-18 18:22:50   29          Null
CBOWLEG   L00000968927  2014-08-18 18:43:03   2014-08-18 18:38:45   4    2014-08-18 18:45:55    
CBOWLEG   L00000968965  2014-08-18 18:52:20   2014-08-18 18:45:55   9    2014-08-18 18:54:50
CBOWLEG   L00000969024  2014-08-18 18:58:24   2014-08-18 18:54:50   3    2014-08-18 19:00:48
CBOWLEG   L00000969068  2014-08-18 19:16:23   2014-08-18 19:00:48   51   2014-08-18 19:00:48
CBOWLEG   L00000969170  2014-08-18 19:22:45   2014-08-18 19:19:45       7    2014-08-18 19:24:34
CBOWLEG   L00000969194  2014-08-18 20:07:41   2014-08-18 19:24:34   73

使用滞后函数我想得到每个用户每次加载后续加载的开始时间。