How to caluate the date Difference in Oracle

Dear Expert,

      I have a table  employee_attendance which keeps track the time_in,time_out (they are date format in database) for an employee every day.There is a third attribute  called workhours(calculated attribute actually),  which calculates  the workhours between these two time_in, time_out, and round the difference to quarter, for example, if the employee works 18minutes(0.3hrs), that should be 0.5hrs(two quarters).

The presentation of the result should be like this:

time_in                   time_out                work_hours
11/07/2003  08:00   11/07/2003 09:13     1.25
11/10/2003  10:55   11/10/2003 11:13      0.5

Please tell me how to write the formula for the caluated attribute -  workhours?


Who is Participating?
Mark GeerlingsDatabase AdministratorCommented:
Which version of Oracle do you have?  Oracle9i includes many more built-ins for dates and times than earlier versions of Oracle.

I wrote a PL\SQL function some years ago that works with Oracle7 and 8 to calculate the time between two dates.  I'll post that here, but it does not round to the nearest 1/4 hour.  You would need to modify it to get that effect.  I think if you divide the hours by 60 (to get the number of minutes), then add 7.5 minutes(to get the effect of rounding up to the nearest quarter hour), then divide by 15, rounded to 0 (to get the number of quarter hours) then divide that by four, rounded to two digits, you should get the number of hours to the nearest quarter hour.

create or replace function time_between (start_tm in date, end_tm in date,
   hours_only varchar2 default 'N') return varchar2 as
-- If "hours_only" is null or "N", the return will be a string formatted like:
--     2 days, 3 hrs, 5 mins, 10 secs
-- If "hours_only" is not "N", then the return is a value in hours, like 102.325
  ret_val   varchar2(80);
  start_sec number;
  end_sec   number;
  full_sec  number;
  balance   number;
  minutes   number;
  hours     number;
  days      number;
  function get_sec (time_in in date) return number as
    return to_number(to_char(time_in,'SSSSS'));
  start_sec := get_sec(start_tm);
  end_sec := get_sec(end_tm);
  -- check if end time is in the same day as start time
  if to_char(start_tm,'YYMMDD') = to_char(end_tm,'YYMMDD') then
    full_sec := end_sec - start_sec;
    days := 0;
    days := trunc(end_tm - start_tm);
    if days > 0 then
      ret_val := to_char(days)||' days, ';
    end if;
    if end_sec > start_sec then
      full_sec := end_sec - start_sec;
      full_sec := 86400 - start_sec + end_sec;
    end if;
  end if;
  if upper(hours_only) = 'N' then
    if full_sec > 3599 then
      hours := floor(full_sec / 3600);
      balance := mod(full_sec,3600);
      full_sec := balance;
      if hours > 1 then
        ret_val := ret_val || to_char(hours) ||' hrs, ';
        ret_val := ret_val || to_char(hours) ||' hr, ';
      end if;    
    end if;
    if full_sec > 59 then
      minutes := floor(full_sec / 60);
      balance := mod(full_sec,60);
      full_sec := balance;
      if minutes > 1 then
        ret_val := ret_val||to_char(minutes)||' mins, ';
        ret_val := ret_val||to_char(minutes)||' min, ';
      end if;    
    end if;
    ret_val := ret_val||to_char(full_sec)||' secs';
    -- Calculate the time difference in hours, to three decimal places
    ret_val := to_char((24 * days) + round((full_sec / 3600),3));
  end if;
  return ret_val;
grant execute on time_between to public;
create public synonym time_between for time_between;
try this:

create table test3(
time_in date, time_out date);

insert into test3
values(to_date('11/07/2003  08:00','mm/dd/yyyy hh24:mi'),
to_date('11/07/2003 09:13','mm/dd/yyyy hh24:mi'));
insert into test3
values(to_date('11/10/2003  10:55','mm/dd/yyyy hh24:mi'),
to_date('11/10/2003 11:13','mm/dd/yyyy hh24:mi'));

insert into test3
values(to_date('11/10/2003  10:55','mm/dd/yyyy hh24:mi'),
to_date('11/11/2003 11:13','mm/dd/yyyy hh24:mi'));
insert into test3
values(to_date('11/10/2003  08:00','mm/dd/yyyy hh24:mi'),
to_date('11/10/2003 16:30','mm/dd/yyyy hh24:mi'));

floor(time_out - time_in)*24 + floor((time_out - time_in-floor(time_out - time_in) )*24)+
decode( floor( ( ((time_out - time_in)*24 - FLOOR((time_out - time_in)*24))*60+14 )/15 ),

hi try this simple formula

select  (dur*60+(15 - round(mod((dur*60),15))))/60
from (
select (time_out -time_in) *24 dur
 from employee_attendance )

and then you can use the out_put to replace the work_hours

What about this?  It seems to satisfy your requirement.  I have set it up as an update statement.

UPDATE employee_attendance
SET work_hours = CEIL(((time_out - time_in) * 24 * 60)/15)*15/60
WHERE <criteria goes here>
Mark GeerlingsDatabase AdministratorCommented:
Hello huer.  Are you checking the responses to your question?  As you can see, there is no simple way to get what you asked for, but you have a few options here to choose from.  Have you tried them?
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