Problem with Creating Chart

Question

Hi ,
I have following query which returns the result as shown below. I want to make a chart w.r.t day showing me the times but i get error "unable to parse query".
Can you please help me?
select null as link
,to_char (START_DATE, 'dd/mm/yyyy') dated
, to_char(to_date('00:00:00','HH24:MI:SS') +
(end_date -start_date), 'HH24:MI:SS') time_diff
from loads_log
where load_id = 3 and success_flag = 'Y' and start_date > sysdate - 25
order by start_date;
Date Time_Diff
06/02/2012     03:25:37
07/02/2012     07:57:33
08/02/2012     06:43:07
09/02/2012     08:47:11
10/02/2012     05:02:07
11/02/2012     05:04:22
12/02/2012     05:41:47
Many thanks
Oz

Answer 1

I have even modified the query to return numeric value instead of time but still same error
date time_diff
06/02/2012     3.25
07/02/2012     7.57
08/02/2012     6.43
09/02/2012     8.47
10/02/2012     5.02
11/02/2012     5.04
select null as link
,to_char (START_DATE, 'dd/mm/yyyy') dated
, to_number(to_char(to_date('00.00','HH24.MI') + (end_date -start_date), 'HH24.MI') )time_diff
from loads_log
where load_id = 3 and success_flag = 'Y' and start_date > sysdate - 25
order by start_date;