oracle sql Time to Resolve Calculation - sql

Question

I have a question and hopefully someone can help, because i have been stuck on this for a long time.
I have a column with remaining minutes for a task to expire and i want to calculate when this task will expire within the business days timeframe starting from the current sysdate day lets say weekdays from 09:00 to 17:00.
| Task No | Minutes Remaining | Expiration date |
| Task1 | 1800 | 27-10-16 9:45 AM |
| Task2 | 3400 | 28-10-16 9:45 AM |
| Task3 | 400 | 29-10-16 9:45 AM |
| Task4 | 180 | 30-10-16 9:45 AM |
| Task5 | 8400 | 31-10-16 9:45 AM |
| Task6 | 5000 | 1-11-16 9:45 AM |

Answer 1

OK, this was a fun problem. To summarize: You are given a date (which in Oracle always includes the time-of-day) from which you start measurement, and an initial duration in minutes. You need to find the expiration date (meaning date and time-of-day as always), which is calculated by adding the duration in minutes to the "clock-starting" date, but the clock should only run during business hours - 9 to 17, Monday to Friday only (not on weekends).
I assume if the "minutes remaining" is 0, then the expiration should be the same as the "clock-starting" date if it falls within work hours, or 9 am on the next work day otherwise.
To understand the solution, let's break it down in two parts. First let's consider a very special case: the "clock starts" on a Monday at 9 am. Then break down minutes remaining into an integer multiple of 2400 (5*8*60 = 2400 minutes in a full work week), plus an integer multiple of 480 from what's left (480 minutes to a work day), plus whatever is left, if anything. Then: the expiration date is the "clock-starting" date, plus however many weeks, plus however many whole days (between 0 and 4), plus the remaining minutes. One exceptional case here: if the "minutes remaining" is an exact multiple of 480 minutes, then expiration is at 5 pm on a certain work day, and not 9 am on the next work day. This requires special handling in the formula. All this is done in the outer query (at the bottom of the solution below).
Then we need to reduce the general case to this special case. This is done in the subquery prep in the solution. I simply increase the "minutes remaining" by the work minutes elapsed from 9 am on Monday at the beginning of the week. This is a relatively simple computation. Note that if the "clock starting" date is after 5 pm on a Friday (or any time on Saturday or Sunday), I must add exactly 2400 minutes, a full work week.
In the solution, I show a variety of "clock starting" dates, dt, and minutes remaining, rm. I tested a variety of situations, and I think the solution is correct, but you may want to test on more data (other situations I didn't include in the tests).
with
inputs ( task, min_rem, dt ) as (
select 'Task1', 1800, to_date('27-10-16 9:45 AM', 'dd-mm-yy hh:mi AM') from dual union all
select 'Task2', 3400, to_date('28-10-16 9:45 AM', 'dd-mm-yy hh:mi AM') from dual union all
select 'Task3', 400, to_date('29-10-16 3:45 AM', 'dd-mm-yy hh:mi AM') from dual union all
select 'Task4', 180, to_date('30-10-16 9:45 AM', 'dd-mm-yy hh:mi AM') from dual union all
select 'Task5', 8400, to_date('31-10-16 9:45 PM', 'dd-mm-yy hh:mi AM') from dual union all
select 'Task6', 5000, to_date('01-11-16 5:00 PM', 'dd-mm-yy hh:mi AM') from dual union all
select 'Task7', 0, to_date('01-12-16 5:00 PM', 'dd-mm-yy hh:mi PM') from dual
),
prep ( task, min_rem, dt, adj_min, adj_dt ) as (
select task, min_rem, dt,
min_rem + case when dt > trunc(dt, 'iw') + 5 + 17/24 then 2400
else (trunc(dt) - trunc(dt, 'iw')) * 480 +
least(480, greatest(0, 1440 * (dt - trunc(dt) - 9/24)))
end,
trunc(dt, 'iw') + 9/24
from inputs
)
select task, min_rem, dt,
adj_dt + 7 * trunc(adj_min / 2400)
+ case when adj_min/480 = trunc(adj_min/480)
then mod(adj_min, 2400) / 480 - 1 + 8/24
else trunc(mod(adj_min, 2400) / 480) + mod(adj_min, 480) / 1440
end as expiration
from prep
order by task
;
Output:
TASK MIN_REM DT EXPIRATION
----- ---------- ----------------- -----------------
Task1 1800 27-10-16 09:45 AM 01-11-16 03:45 PM
Task2 3400 28-10-16 09:45 AM 08-11-16 10:25 AM
Task3 400 29-10-16 03:45 AM 31-10-16 03:40 PM
Task4 180 30-10-16 09:45 AM 31-10-16 12:00 PM
Task5 8400 31-10-16 09:45 PM 24-11-16 01:00 PM
Task6 5000 01-11-16 05:00 PM 16-11-16 12:20 PM
Task7 0 01-12-16 05:00 PM 01-12-16 05:00 PM
7 rows selected