Question

I’d like the sum of TotalVisitedTime time but it is alias column so how can I gtt it?

Select CONVERT(varchar(6), DATEDIFF(second, [Start], [End])/3600)
   + ':'
   + RIGHT('0' + CONVERT(varchar(2), (DATEDIFF(second, [Start], [End]) % 3600) / 60), 2)
   + ':'
   + RIGHT('0' + CONVERT(varchar(2), DATEDIFF(second, [Start], [End]) % 60), 2) AS TotalVisitedTime
FROM [Table Name]

Note: [Start] and [End] are columns name.

Answer 1

SELECT SUM(TotalVisitedTime)
FROM (    
    -- AS PER @Alex Aza,  @Andriy M     
        SELECT 1234 AS TotalVisitedTime
     ) AS OuterTable