How to Automate Deficit Value to Next Month Target? - mysql

Question

I have a data table as shown below
Owner
Month
Year
Target
Achieved
A
April
2021
100
50
B
April
2021
100
80
A
May
2021
100
80
B
May
2021
100
130
A
June
2021
100
50
B
June
2021
100
60
The logic is if there is a shortfall with respect to Achieved then the shortfall amount should be added to next month target.
For Example A's April Target is 100 and Achieved is 50. The Shortfall would be 100-50=50. The 50 should be added to May Target
The output required as
Owner
Month
Year
Target
Achieved
Shortfall(Target-Achieved)
A
April
2021
100
50
50
A
May
2021
150
80
70
A
June
2021
170
50
120
B
April
2021
100
80
20
A
May
2021
120
130
-10
B
June
2021
100
60
40
Is it possible to achieve this automation in SQL?
Thanks

Answer 1

You want a cumulative sum. Assuming that the month column is really ordered, then the final column is:
select t.*,
sum(target - achieved) over (partition by owner, year
order by month
)
from t;
You can use this for the calculation for the new target:
select t.*,
sum(target - achieved) over (partition by owner, year
order by month
)
(achieved +
sum(target - achieved) over (partition by owner, year
order by month
)
) as new_target
from t;

Answer 2

Consider year wise all month as ordering purpose if data available. If previous short fall is negative then current row short fall will be calculated as target - achieved otherwise target + prev.shortfall - achieved.
-- MySQL(v5.8)
SELECT t.owner, t.month, t.year
, t.target + (CASE WHEN t.row_num = 1 THEN 0
ELSE CASE WHEN LAG(short_fall) OVER (PARTITION BY t.owner ORDER BY t.row_num) < 0
THEN 0
ELSE LAG(short_fall) OVER (PARTITION BY t.owner ORDER BY t.row_num)
END
END) target
, t.achieved
, CASE WHEN LAG(short_fall) OVER (PARTITION BY t.owner ORDER BY t.row_num) < 0
THEN t.target - t.achieved
ELSE short_fall
END short_fall
FROM (select owner, month
, year
, target
, achieved
, SUm(target - achieved) OVER
(PARTITION BY owner, year ORDER BY DATE_FORMAT(STR_TO_DATE(CONCAT(month, ' 1, ', year),'%M %d,%Y'), '%c')) short_fall
, ROW_NUMBER() OVER
(PARTITION BY owner, year ORDER BY DATE_FORMAT(STR_TO_DATE(CONCAT(month, ' 1, ', year),'%M %d,%Y'), '%c')) row_num
from test) t;
Please check from url https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=3e114348c2d92015490f76fdbab1c46f