Question

I have a table where each row has a start and stop date-time. These can be arbitrarily short or long spans.

I want to query the sum duration of the intersection of all rows with two start and stop date-times.

How can you do this in MySQL?

Or do you have to select the rows that intersect the query start and stop times, then calculate the actual overlap of each row and sum it client-side?

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To give an example, using milliseconds to make it clearer:

Some rows:

ROW  START  STOP
1    1010   1240
2     950   1040
3    1120   1121

And we want to know the sum time that these rows were between 1030 and 1100.

Lets compute the overlap of each row:

ROW  INTERSECTION
1    70
2    10
3     0

So the sum in this example is 80.

Answer 1

If your example should have said 70 in the first row then

assuming @range_start and @range_end as your condition paramters:

SELECT SUM( LEAST(@range_end, stop) - GREATEST(@range_start, start) )
FROM Table
WHERE @range_start < stop AND @range_end > start

using the greatest/least and date functions you should be able to get what you need directly operating on the date type.