sql server - How can I get the sum of multiple datetime values?

Question

I have a query such that the query's result is:

SELECT CONVERT(VARCHAR(8),(MAX(END_TIME)-MIN(START_TIME)),108) as DURATION WHERE ... GROUP BY TITLE

For each title, DURATION is different. The query returns:

DURATION
00:16:14
00:00:00
00:01:30
00:16:25
00:09:34
00:00:01
01:04:04
00:00:28
00:00:12
00:06:11
00:26:38
00:31:44
00:02:16
00:03:22
00:09:39
00:03:20
00:03:43
00:09:33
00:08:05
00:06:58
00:25:29
01:55:30
00:03:02
00:00:18
00:06:09
00:07:26
00:25:43
00:00:16
00:26:58
02:09:38
00:57:56
00:00:45
00:00:00
00:07:24
00:00:54
00:00:27
00:01:28
00:07:14
00:00:19
01:43:25
00:58:23
00:02:29
02:19:48
00:09:06
05:12:15
02:27:15
00:56:47
00:02:24

I need the sum of these values; how can I get it?

Answer 1

Convert minutes into seconds

SUM() the seconds

Convert back to minutes

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The following will give you the SUM of seconds:

SET @Seconds = SELECT SUM(DATEDIFF(SECOND, [START_TIME], [END_TIME]))

The following then turns that into a datetime object:

select convert(varchar(8), dateadd(second, @Seconds, 0),  108)

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Or as 1 query:

SELECT convert(varchar(8), dateadd(second, SUM(DATEDIFF(SECOND, [START_TIME], [END_TIME])), 0),  108)