sql - DATEDIFF in HH:MM:SS format

Question

I need to calculate the total length in terms of Hours, Minutes, Seconds, and the average length, given some data with start time and end time.

For example the result must be something like 45:15:10 which means 45 hours 15 min 10 sec, or 30:07 for 30 min 07 sec.

We're using SQL Server 2008 R2 and the conversion failed when time is more than 24:59:59. Any idea of how I could do this?

For information, the columns in the table are Id, StartDateTime, EndDateTime, etc. I need to make a monthly report which contains the recordings count of the month, the total length of these records, and the average length. I'd like to know if there is an easy way to perform all of this.

Answer 1

You shouldn't be converting to time - it is meant to store a point in time on a single 24h clock, not a duration or interval (even one that is constrained on its own to < 24 hours, which clearly your data is not). Instead you can take the datediff in the smallest interval required (in your case, seconds), and then perform some math and string manipulation to present it in the output format you need (it might also be preferable to return the seconds to the application or report tool and have it do this work).

DECLARE @d TABLE
(
  id INT IDENTITY(1,1), 
  StartDateTime DATETIME, 
  EndDateTime DATETIME
);

INSERT @d(StartDateTime, EndDateTime) VALUES 
(DATEADD(DAY, -2, GETDATE()), DATEADD(MINUTE, 15, GETDATE())),
(GETDATE()                  , DATEADD(MINUTE, 22, GETDATE())),
(DATEADD(DAY, -1, GETDATE()), DATEADD(MINUTE,  5, GETDATE())),
(DATEADD(DAY, -4, GETDATE()), DATEADD(SECOND, 14, GETDATE()));

;WITH x AS (SELECT id, StartDateTime, EndDateTime, 
  d = DATEDIFF(SECOND, StartDateTime, EndDateTime),
  a = AVG(DATEDIFF(SECOND, StartDateTime, EndDateTime)) OVER()
  FROM @d
)
SELECT id, StartDateTime, EndDateTime,
  [delta_HH:MM:SS] = CONVERT(VARCHAR(5), d/60/60)
  + ':' + RIGHT('0' + CONVERT(VARCHAR(2), d/60%60), 2)
  + ':' + RIGHT('0' + CONVERT(VARCHAR(2), d % 60), 2),
  [avg_HH:MM:SS] = CONVERT(VARCHAR(5), a/60/60)
  + ':' + RIGHT('0' + CONVERT(VARCHAR(2), a/60%60), 2)
  + ':' + RIGHT('0' + CONVERT(VARCHAR(2), a % 60), 2)
FROM x;

Results:

id  StartDateTime        EndDateTime          delta_HH:MM:SS  avg_HH:MM:SS
--  -------------------  -------------------  --------------  ------------
1   2013-01-19 14:24:46  2013-01-21 14:39:46  48:15:00        42:10:33
2   2013-01-21 14:24:46  2013-01-21 14:46:46   0:22:00        42:10:33
3   2013-01-20 14:24:46  2013-01-21 14:29:46  24:05:00        42:10:33
4   2013-01-17 14:24:46  2013-01-21 14:25:00  96:00:14        42:10:33

This isn't precisely what you asked for, as it won't show just MM:SS for deltas < 1 hour. You can adjust that with a simple CASE expression:

;WITH x AS (SELECT id, StartDateTime, EndDateTime, 
  d = DATEDIFF(SECOND, StartDateTime, EndDateTime),
  a = AVG(DATEDIFF(SECOND, StartDateTime, EndDateTime)) OVER()
  FROM @d
)
SELECT id, StartDateTime, EndDateTime,
  [delta_HH:MM:SS] = CASE WHEN d >= 3600 THEN 
    CONVERT(VARCHAR(5), d/60/60) + ':' ELSE '' END
  + RIGHT('0' + CONVERT(VARCHAR(2), d/60%60), 2)
  + ':' + RIGHT('0' + CONVERT(VARCHAR(2), d % 60), 2),
  [avg_HH:MM:SS] = CASE WHEN a >= 3600 THEN 
    CONVERT(VARCHAR(5), a/60/60) + ':' ELSE '' END
  + RIGHT('0' + CONVERT(VARCHAR(2), a/60%60), 2)
  + ':' + RIGHT('0' + CONVERT(VARCHAR(2), a % 60), 2)
FROM x;

This query changes the delta column in the 2nd row in the above result from 0:22:00 to 22:00.