How to Correct this Select Statement...?

Question

hi all
i wrote a select as follows
select datediff('HH',to_date(job_start,'hh24:mi:ss'),to_date('15:29:59','hh24:MI:ss')) from shift
requirement is to calculate the hours used in a shift, the job_start column is date type and having value '23/08/2007 07:00:00' , and the second one is the shift end time. so it should give 8.5 hrs as the result. but it is throwing error ORA--1858 non-numeric char found where a numeric expected. datediff function is taken from Ask Tom discussion forums.
any idea...?
regards
Kris

Answer 1

I think i cant, this is to be done for every day...so
is there any way i can set the time of the current
date to '15:29:59'..?
SQL> ed
Wrote file afiedt.buf
  1  with t as (select to_date('23/08/2007 08:30:00','dd/mm/yyyy hh24:mi:ss') as start_time from dual)
  2  -- end of test data
  3  select (to_date(to_char(sysdate,'dd/mm/yyyy')||'  15:29:59','dd/mm/yyyy hh24:mi:ss')-start_time)*24 as hrs
  4* from t
SQL> /
       HRS
6.99972222
SQL>