use this query i think it will solve your problem
Declare @fromdt datetime
Declare @todt datetime
set @fromdt=CONVERT(datetime,2012-05-30 ,105)
set @todt =CONVERT(datetime,2012-05-31 ,105)
SELECT
(case when datediff(DAY,@fromdt ,@todt ) >0 then datediff(DAY,@fromdt ,@todt ) else abs(datediff(DAY,@fromdt ,@todt )) end)as 'DaysDifference'
if you don't want to check datediffernce is >0 or <=0 then you can use direct abs() method as per describe in solution 1.