Hi
You wont be able to store 1.5 into in integer field, it would get rounded off to 1 you might want to store it as a decimal number
Also should 1 hour and 30 min not be rounded off to 1.5? In which case the following would work for you.
DECLARE @startTime DATETIME = '2015-07-10 10:15:00.000'
DECLARE @EndTime DATETIME = '2015-07-10 11:45:00.000'
SELECT DATEDIFF(mi,@startTime,@EndTime)/60.0
If you are sure that that is the format you want then you can just concatenate the fields
DECLARE @startTime DATETIME = '2015-07-10 10:15:00.000'
DECLARE @EndTime DATETIME = '2015-07-10 11:20:00.000'
SELECT cast(DATEDIFF(HH,@startTime,@EndTime) as varchar(10)) +'.'+cast((DATEDIFF(mi,@startTime,@EndTime)%60) as varchar(2))