Postgres: Adjust monthly calculations based on goals set - sql

Question

Below is my table:
practice_id | practice_name | practice_location | practice_monthly_revenue | practice_no_of_patients | date
-------------+-------------------+-------------------+--------------------------+-------------------------+---------------------
6 | Practice Clinic 1 | Location1 | 10000 | 8 | 2016-01-12 00:00:00
7 | Practice Clinic 1 | Location1 | 12000 | 10 | 2016-02-12 00:00:00
8 | Practice Clinic 1 | Location1 | 8000 | 4 | 2016-03-12 00:00:00
9 | Practice Clinic 1 | Location1 | 15000 | 10 | 2016-04-12 00:00:00
10 | Practice Clinic 1 | Location1 | 7000 | 3 | 2016-05-12 00:00:00
11 | Practice Clinic 2 | Location2 | 15000 | 12 | 2016-01-13 00:00:00
12 | Practice Clinic 2 | Location2 | 9000 | 8 | 2016-02-13 00:00:00
13 | Practice Clinic 2 | Location2 | 5000 | 2 | 2016-03-03 00:00:00
14 | Practice Clinic 2 | Location2 | 12000 | 9 | 2016-04-13 00:00:00
----------------------------------------------------------------------------------------------------------------------------------
I am firing below query to get monthly revenue vs monthly goal:-
select [date:month], SUM(practice_monthly_revenue) as Monthly_Revenue, 100000/12 as Goals
from practice_info
where practice_name IN ('Practice Clinic 1')
group by [date:month], practice_name
ORDER BY [date:month] ASC
Where "Monthly_Revenue" refers to exact revenue every month while Goal was the exact revenue expected to be generated.
Now I am having issue to write a sql query to adjust the goals next month if the goals aren't met.
E.g. if in March the revenue generated is below 8k which is the monthly goal then the remaining amount in goal should be adjusted in next months goal.
Will it be possible to achieve this with a sql query or I will have to write a sql procedure for it?
EDIT:- I forgot to add that the db belong to postgres.

Answer 1

Goals can be counted as
with recursive goals(mon, val, rev) as
(select min([pinf.date:month]) as mon /* Starting month */, 8000 as val /* Starting goal value */, pinf.practice_monthly_revenue as rev
from practice_info pinf
where pinf.practice_name IN ('Practice Clinic 1')
union all
select goals.mon + 1 as mon, 8000 + greatest(0, goals.val - goals.rev) as val, pinf.practice_monthly_revenue as rev
from practice_info pinf, goals
where goals.mon + 1 = [pinf.date:month]
and pinf.practice_name IN ('Practice Clinic 1')
)
select * from goals;
Just integrate it with your query to compare goals and revenues. It can be not exactly what you want, but I do believe you'll get the main point.