Calculating difference between two times

[karlomutschler]

good day
We wish to subtract the
CURR_TIME(Jobname_01) from
CURR_TIME(Jobname_02)
and update the column DURATION((Jobname_02) with the result.

Excerpt from the DATALOAD_EXEC_LOG Table:

CURR_DATE DATE FORMAT 'YY/MM/DD',
CURR_TIME CHAR(8),
DURATION CHAR(8),
JOBNAME VARCHAR(64)

CURR_DATE CURR_TIME DURATION JOBNAME
========= ========= ======== =======
22.11.2011 09:36:10 00:02:51 Jobname_02
22.11.2011 09:33:59 ? Jobname_01

This works!
UPDATE DATALOAD_EXEC_LOG
SET DURATION = CAST('09:36:10' - '09:33:59' AS TIME(0))
WHERE CURR_DATE = DATE
AND JOBNAME = 'Jobname_02'

Difference = 00:02:51

UPDATE DATALOAD_EXEC_LOG
SET DURATION = CAST(
(SELECT CURR_TIME FROM DATALOAD_EXEC_LOG
WHERE CURR_DATE = DATE
AND JOBNAME = 'Jobname_02')
-
(SELECT CURR_TIME FROM DATALOAD_EXEC_LOG
WHERE CURR_DATE = DATE
AND JOBNAME = 'Jobname_01')
)AS TIME(0))
WHERE CURR_DATE = DATE
AND JOBNAME = 'Jobname_02';

This does not work!
Error Message: Invalid operation on an ANSI Datetime or Interval value

Any help much appreciated
Kindest regards
Karlo