How to calculate day specific data from accumulated data - oracle

Question

I have an Oracle table with values for two accounts and each record will have Date field. First day of the week will have only data relevant to the Day 1 but when we see the data for Day2 in a week it has accumulated data. So we need to subtract Day2 data from previous day data to calculate exact data for Day2.Similar approach for Day3..Day7.
Please suggest the best approach in SQL query to handle this requirement. I am very sorry to bother you. I am totally new to SQL.Really appreciate your valuable inputs.As an example, there are 6 columns with header are given below
Center Entity Bonus Year Period Incentive
MANUFACTURING NEW YORK 1200 FY18 31-12-2017 120
MANUFACTURING NEW YORK 1500 FY18 01-01-2018 250
MANUFACTURING NEW YORK 1800 FY18 01-01-2018 320
So assuming Dec 31, 2017 is the first day of the week, the data record will show only data for that day 1. When we move on to Day 2 of the week i.e. Jan 01, 2018, it has accumulated data which includes Day 1 and day2. So we need to subtract Day2 data from Day1 data to calculate exact data for data 2. 1500 - 1200 = 300 is the exact value for Day 2. Similar approach we need to follow for Day3, day4, Day5,Day6 and Day7.
Expected output is given below
Center Entity Bonus Year Period Incentive
MANUFACTURING NEW YORK 1200 FY18 01-01-2018 120
MANUFACTURING NEW YORK 300 FY18 01-01-2018 130
MANUFACTURING NEW YORK 300 FY18 01-01-2018 70

Answer 1

You could use a simple LAG() function with NVL().
select Center, Entity, Bonus,Year,Period,
Incentive - NVL( LAG(Incentive , 1) OVER ( ORDER BY Period ), 0) Incentive
FROM yourtable;
DEMO

Answer 2

You can do a self join with you table on period and do the subtraction from previous date's data.
looks like you have typo in the test data and result, the dates should be incremental as stated in description, but it has duplicate.
SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE t
(Center varchar2(13), Entity varchar2(8), Bonus int, Year varchar2(4), Period DATE, Incentive int)
;
INSERT INTO t (Center, Entity, Bonus, Year, Period, Incentive)
VALUES ('MANUFACTURING', 'NEW YORK', 1200, 'FY18', DATE '2017-12-31', 120);
INSERT INTO t (Center, Entity, Bonus, Year, Period, Incentive)
VALUES ('MANUFACTURING', 'NEW YORK', 1500, 'FY18', DATE '2018-01-01', 250);
INSERT INTO t (Center, Entity, Bonus, Year, Period, Incentive)
VALUES ('MANUFACTURING', 'NEW YORK', 1800, 'FY18', DATE '2018-01-02', 320);
;
Query:
select t1.center,
t1.entity,
t1.bonus - nvl (t2.bonus,0) bonus,
t1.year,
t1.period,
t1.incentive - nvl(t2.incentive,0) incentive
from t t1
left outer join t t2
on t1.period = t2.period + 1
order by t1.period
Results:
| CENTER | ENTITY | BONUS | YEAR | PERIOD | INCENTIVE |
|---------------|----------|-------|------|----------------------|-----------|
| MANUFACTURING | NEW YORK | 1200 | FY18 | 2017-12-31T00:00:00Z | 120 |
| MANUFACTURING | NEW YORK | 300 | FY18 | 2018-01-01T00:00:00Z | 130 |
| MANUFACTURING | NEW YORK | 300 | FY18 | 2018-01-02T00:00:00Z | 70 |