how to get hours from subtracting two date time values in SQL Server 2005

I have two date values: 08/6/2009 00:00:00 and 10/6/2009 23:59:59.

How do I get the difference in hours in a query in SQL Server 2005?

From stackoverflow

• SELECT  DATEDIFF(hour, '2009-08-06 00:00:00', '2009-10-06 23:59:59')
  
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• DATEDIFF(HOUR,'08/6/2009 00:00:00','10/6/2009 23:59:59')