Q. How to find hour between two time?

DECLARE @StartTime DATETIME = '2011-09-23 15:00:00'
       ,@EndTime   DATETIME = '2011-09-23 17:54:02'
       
SELECT CONVERT(VARCHAR(8), DATEADD(SECOND, DATEDIFF(SECOND,@StartTime, @EndTime),0), 108) as ElapsedTime