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
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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)