Get Time difference from same report column

Summary

Get time difference for same incident ID but in same column

Content

Hi

I have incident ID and Adjusted time column in same report. Same incident ID has two time records. One is start time and another record is for end time. I need to get the total time agent spent on this incident. Here is an example 

Incident ID        Adjusted Time      Difference

100                   07 : 00 AM            

100                   07:30 AM            30 Minutes

 

How to get date time difference from same column. I tried using date_diff() & date_group()  but did not get require result.

Does anyone has an idea how to get this difference

Thanks!!