Running sum with max and min cap in SQL Server - sql

Question

I have a table that looks like this
|ID1| ID2| Date |count |
+---+----+------------+------+
|1 | 1 | 2019-07-24 | 3 |
|1 | 1 | 2019-07-25 | 3 |
|1 | 1 | 2019-07-26 | 3 |
|1 | 1 | 2019-07-27 | 1 |
|1 | 1 | 2019-07-28 | -3 |
|1 | 2 | 2019-07-24 | 1 |
|1 | 2 | 2019-07-25 | -3 |
|1 | 2 | 2019-07-26 | 3 |
|1 | 2 | 2019-07-27 | 3 |
|1 | 2 | 2019-07-28 | 3 |
I am interested in calculating the running sum with a min cap of 0 and a max cap of 8. Resulting table would look like this.
|ID1| ID2| Date |count |runningSum|
+---+----+------------+------+----------+
|1 | 1 | 2019-07-24 | 3 | 3 |
|1 | 1 | 2019-07-25 | 3 | 6 |
|1 | 1 | 2019-07-26 | 3 | 8 |
|1 | 1 | 2019-07-27 | 1 | 8 |
|1 | 1 | 2019-07-28 | -3 | 5 |
|1 | 2 | 2019-07-24 | 1 | 1 |
|1 | 2 | 2019-07-25 | -3 | 0 |
|1 | 2 | 2019-07-26 | 3 | 3 |
|1 | 2 | 2019-07-27 | 3 | 6 |
|1 | 2 | 2019-07-28 | 3 | 8 |
I know that Oracle has many different solution to address this problem, like
described here in number 7
https://blog.jooq.org/2016/04/25/10-sql-tricks-that-you-didnt-think-were-possible/. Does anything as simple as this exist for Microsoft SQL Server.
Note that I am not allowed to create tables, temporary tables or table variables.
EDIT I am using Azure Datawarehouse where recursive CTE and cursor statements are not available. Are there really not any other ways to solve this problem in SQL Server?

Answer 1

I don't think you can do this with window functions, alas. The problem is that the caps introduce a state change, so you have to process the rows incrementally to get the value for a given row.
A recursive CTE does iteration, so it can do what you want:
with t as (
select t.*,
row_number() over (partition by id1, id2 order by date) as seqnum
from <yourtable> t
),
cte as (
select id1, id2, date, count,
(case when count < 0 then 0
when count > 8 then 8
else count
end) as runningsum,
seqnum
from t
where seqnum = 1
union all
select cte.id1, cte.id2, t.date, t.count,
(case when t.count + cte.runningsum < 0 then 0
when t.count + cte.runningsum > 8 then 8
else t.count + cte.runningsum
end) as runningsum, t.seqnum
from cte join
t
on t.seqnum = cte.seqnum + 1 and
t.id1 = cte.id1 and t.id2 = cte.id2
)
select *
from cte
order by id1, id2, date;
Here is a db<>fiddle.
Note that very similar code will work in Oracle 12C, which supports recursive CTEs. In earlier versions of Oracle, you can use connect by.