Time Comparison

Question

Dear Friends,
I need your valuable suggestion to proceed.
Functional Flow :-
My client will have a Construction project with a budgeted hours to finish and the Manager will assign Employees to this project. they need to know all the budgted hours are allocated to Employees to finish the work.
Technical
for example the budgeted hour will be in the format of 50:30 (Means 50 hrs and 30 minutes) and Workers will be allocated to this project like
Monday 8:00 to 17:15
Tuesday 9:00 to 16:45
Tables := Projects Column Budgeted_hours varchar2(6)
Assignments Column Allocated_hours varchar2(6)
My question is how to compare the budgeted hours and allocated_hours of the workers to see whether all the budgeted hours are allocated to workers as I am storing these all values in Varchar2. Why I am using Varchar2 is that, they want to have this ':' sign with time slot.
Can anyone help me how to do this. Whether I need to change varchar to Date ? if so the data will be inserted with date and time which is not correct for this situvation. Need help
Please write to me at [email protected]
Regards
SJK
thanks
Sjk

Answer 1

I would suggest you store elapsed time as a number of days e.g. 50:30 hours = 50.5/24 days = 2.1041666667 days. You'd need to write some simple PL/SQL database functions to parse and convert data between the numeric stored format and the desired input/output character format. The reasons for this are
1) arithmetic becomes simple e.g. adding another 8 hours to the budgeted 50.5 hours
2) where appropriate, it coincides with Oracle's way of handling date arithmetic (the difference between two DATEs is a NUMBER of days.
If you can determine an employee's total number of allocated hours, then the comparison you mentioned becomes easy: unallocated = budgeted - allocated. You can also
Your problem introduces lots of complexity due to the fact that a project day is not the same as a 24 hour calendar day (e.g. employee shift is only 8 hours, 5 days a week). Any calculation involving start or end dates will have to take the project calendar and work shifts into account. I suggest you invest some deep thought into the fundamental data manipulations needed by your project, and create a package of simple functions and procedures to form the foundation for higher level operations. Here's one example:
FUNCTION SHOW_AS_HHMM (p_durn IN NUMBER) RETURN VARCHAR2 IS
l_hours_n NUMBER;
l_hours_c VARCHAR2(16);
l_minutes_c VARCHAR2(2);
BEGIN
-- convert days into hours
l_hours_n := p_durn * 24;
-- convert hours into characters
l_hours_c := to_char (trunc (l_hours_n));
-- convert fraction of hours into minutes characters
l_minutes_c := to_char (round ((l_hours_n - trunc (l_hours_n)) * 60));
return l_hours_c || ':' || l_minutes_c;
EXCEPTION
WHEN OTHERS THEN
raise;
END show_as_hhmm;