sum of hours between two dates in sql

SELECT
    CONVERT(VARCHAR(6), DATEDIFF(SECOND, '2012-06-26 03:00:00.000', '2012-06-27 23:30:00.000')/3600) + ':'
    + RIGHT('0' + CONVERT(VARCHAR(2), (DATEDIFF(SECOND, '2012-06-26 03:00:00.000', '2012-06-27 23:30:00.000') % 3600) / 60), 2) + ':'
    + RIGHT('0' + CONVERT(VARCHAR(2), DATEDIFF(SECOND, '2012-06-26 03:00:00.000', '2012-06-27 23:30:00.000') % 60), 2)

courtesy Mr.Vanthiya Thevan