declare @StartDate datetime;
declare @EndDate datetime;
select @StartDate = '10/01/2012 08:40:18.000';
select @EndDate='10/04/2012 09:52:48.000';
select cast(datediff(hour,@StartDate,@EndDate) as varchar(10)) + left(right(cast(cast(cast((@EndDate-@StartDate) as datetime) as time) as varchar(16)),14),6)