Wierd behavior of PARTITION BY Over clause with UNBOUNDED PRECEDING

having issue sorting this data last date for every minute of data, while last date for min is coming fine, cant make last bid qty using same method, first_value works though??Seems like a bug, any thoughts?Meanwhile using other methods to get this done.....[code="other"]declare @bidData table (activityDate datetime,BidQtyRaw bigint)insert into @bidData select 'Mar 28 2014 12:03:07:000PM',730384100insert into @bidData select 'Mar 28 2014 12:03:44:000PM',720528600insert into @bidData select 'Mar 28 2014 12:03:45:000PM',720528600insert into @bidData select 'Mar 28 2014 12:19:26:000PM',661768600insert into @bidData select 'Mar 28 2014 12:19:27:000PM',662768600insert into @bidData select 'Mar 28 2014 12:19:28:000PM',670718600insert into @bidData select 'Mar 28 2014 12:19:29:000PM',670718600insert into @bidData select 'Mar 28 2014 12:19:30:000PM',721218600insert into @bidData select 'Mar 28 2014 12:19:32:000PM',724218600insert into @bidData select 'Mar 28 2014 12:50:02:000PM',120538700insert into @bidData select 'Mar 28 2014 12:50:09:000PM',60678700select ActivityDate,datepart(minute,ActivityDate) ActivityMin,BidQtyRaw ,max(BidQtyRaw) OVER ( PARTITION BY datepart(minute,ActivityDate) order by ActivityDate desc Rows UNBOUNDED PRECEDING ) AS BidQtyMin ,first_value(BidQtyRaw) OVER ( PARTITION BY datepart(minute,ActivityDate) order by ActivityDate desc Rows UNBOUNDED PRECEDING ) AS BidQtyMinFirst ,max(ActivityDate) OVER ( PARTITION BY datepart(minute,ActivityDate) order by ActivityDate desc Rows UNBOUNDED PRECEDING ) AS LastActivityDateMinfrom @bidData order by ActivityDate[/code]