# 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?

Thanks,

Huer
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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
begin
end;
--
begin
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;
else
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;
else
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, ';
else
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, ';
else
ret_val := ret_val||to_char(minutes)||' min, ';
end if;
end if;
ret_val := ret_val||to_char(full_sec)||' secs';
else
-- 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;
end;
/
grant execute on time_between to public;
create public synonym time_between for time_between;

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Commented:
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'));

----------------
select
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 ),
0,0,1,0.25,2,0.5,3,0.75)
FROM TEST3

Commented:
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

Commented: