SQL Query Select time within last hour.

SELECT Vehicle_ID
     , Alias
       , Day
       , Month
       , Year
       , GPSTime
       , Date_Time
       , PC_Date
       , PC_Time
       , Street
       , City
       , State
       , Zip_Code
       , Latitude
       , Longitude
       , Speed
       , Course
       , Altitude
       , Event
       , Advisory_Event
       
FROM            dbo.VehicleState
WHERE        (Latitude IS NOT NULL) and Date_Time >= dateadd(hh, -1, getdate())
/* you said you want the latest . . . if there is more than one in the last our this needs to be included, otherwise you can remove below this and just keep the addition in the where condition */
group by     Vehicle_ID
        , Alias
       , Day
       , Month
       , Year
       , GPSTime
       , Date_Time
       , PC_Date
       , PC_Time
       , Street
       , City
       , State
       , Zip_Code
       , Latitude
       , Longitude
       , Speed
       , Course
       , Altitude
       , Event
       , Advisory_Event
having Date_Time  = max(date_time)

I got the following error:

Arithmetic overflow error converting expression to data type datetime.

I looked at our vendors table and they have date_time as an INT, and not DATETIME.  So I tried cast ( date_time as datetime) but still same error.

does GPSTime work or is that another int?

If [date_time] and [GPS_time] are integre then one converts getdate() to int for the comparisons to work.

You mention SQL 2012, so you can use format()

e.g.
       FORMAT(GETDATE(), 'yyyyMMddHHmmss')

and:

cast(FORMAT(GETDATE(), 'yyyyMMddHHmmss') as bigint)
cast(FORMAT(GETDATE(), 'yyyyMMddHHmm') as bigint)

You don't indicate how large the [date_time] or [GPS_time] values are. I have gone down to seconds in the example above (14 digits) and this requires bigint. Removing 'ss' would result in minute precision and 12 digits still needing bigint.
If [date_time] or [GPS_time] values are only 8 digits then you cannot determine "in the last hour" from that/those field/s.

You'd have to give some examples of int datetimes and the corresponding calendar datetime.

Example of all date related info from DB for one row.

Date_Time:
1383595291 int

PC_date:
2013-11-04 varchar(12)

PC_Time:
14:01:33 char(8)

Day:
4 smallint

Month:
11 smallint

Year:
2013 smallint

GPSTime:
50491 float

How do you know that 1383595291 = 11/04/2013?

I thought it was a Julian date but it's not working.  Have you worked with that datetime column in the past?

suggested reading:
DATE and TIME ... don't be scared, and do it right (the first time)

Thanks!!  Based off two posts here is the solution I came up with:

SELECT [Vehicle_ID]
      ,[Day]
      ,[Month]
      ,[Year]
      ,[GPSTime]
      ,[Date_Time]
      ,[PC_Date]
      ,[PC_Time]
      ,[Latitude]
      ,[Longitude]
      ,[Speed]
      ,[Course]
      ,dateadd(second,GPSTime,PC_date) as GPS_Time
 
  FROM [Integrator].[dbo].[VehicleState]

  WHERE LATITUDE > 0 AND dateadd(second,GPSTime,PC_date) >= dateadd(hh, -1, getdate())

  GROUP BY [Vehicle_ID]
      ,[Day]
      ,[Month]
      ,[Year]
      ,[GPSTime]
      ,[Date_Time]
      ,[PC_Date]
      ,[PC_Time]
      ,[Latitude]
      ,[Longitude]
      ,[Speed]
      ,[Course]
      ,dateadd(second,GPSTime,PC_date)