SELECT

OPENDATE, ASSNDATE,

CAST(minutes_diff / 60 AS varchar(3)) + ':' +

RIGHT('0' + CAST(minutes_diff % 60 AS varchar(2)), 2) AS Date_Diff

FROM (

SELECT GETDATE() AS OPENDATE, DATEADD(MINUTE, -9, GETDATE()) AS ASSNDATE UNION ALL -- lt 60 mins

SELECT GETDATE(), DATEADD(MINUTE, -196, GETDATE()) UNION ALL -- gt 60 mins, lt 24 hrs

SELECT GETDATE(), DATEADD(MINUTE, -(24*60+112), GETDATE()) -- gt 24 hrs

) AS test_data

CROSS APPLY (

SELECT DATEDIFF(MINUTE, ASSNDATE, OPENDATE) AS minutes_diff

) AS assign_alias_names_to_calculated_values_1