I have the following query:

SELECT DATE_FORMAT(date_start, '%d/%m/%Y') AS Fdate_start, TIMEDIFF(date_end,date_start) AS calc_duration, type, type_detail, category FROM `delegation` WHERE (date_start >= '$date_start' and date_end <= '$date_end')

I want to be able to add all the calc_duration in the results as total_duration for example.

I tried some solutions with SUM but got nowhere.