Now I would like to calculate the difference in time between Start_datetime and previous Start_datetime, grouped by the column Group. The result would be something like this:
Time since last one
The next step would be to calculate the sum of all "time since last one" over a time dimension (year) and group.
The problem is not to calculate the time difference. I found the functions previous() and peak() for addressing the previous line, and interval() and timestamp() to calculate the difference and display it in any format. However - I can not find out a way to group the lines by the column Group and calculate only the matching lines!
If you could present me a solution or a hint thereof, I would be grateful.