Preventing running total from going negative in Oracle - oracle

Question

Column 'amount' has value 5 in first row, and value -10 in second row.
Is there a way to make oracle's sum(amount) over() function to return 0 instead of -5 for the second row?

Answer 1

Blatantly using Rajesh Chamarthi's example source: but altering to show more negative and positive... and showing how a case would change all the negative to zero while maintaining the other amounts...
with t as (
select 5 as x, 1 as id from dual
union all
select -10, 2 as id from dual
union all
select 7, 3 as id from dual
union all
select -5, 4 as id from dual
union all
select -2, 5 as id from dual
),
B as (select t.x,
case when sum(x) over (order by id) < 0 then 0
else sum(x) over (order by id)
end Amount
from t
order by id)
Select X, Case when amount < 0 then 0 else amount end as Amount from B;
T Amount
5 5
-10 0
7 2
-5 0
-2 0
----Attempt 2 (1st attempt preserved as comments below reference it)
I couldn't figure out how to interrupt the window function to reset the value to 0 when amount fell below 0... so I used a recursive CTE which gave me greater control.
If id's are not sequential, we could add a row_Number so we have an ID to join on... or we could use min() where > oldID. I assumed we have a single key unique ID or some way of "Sorting" the records in the order you want the sum to occur...
with aRaw as (
select 5 as x, 15 as id from dual
union all
select -10, 20 as id from dual
union all
select 7, 32 as id from dual
union all
select 2, 46 as id from dual
union all
select -15, 55 as id from dual
union all
select 3, 68 as id from dual
),
t as (Select A.*, Row_number() over (order by ID) rn from aRAW A),
CTE(RN, ID, x, SumX) AS (
Select T.RN, T.ID, x, X from t WHERE ID = (Select min(ID) from t)
UNION ALL
Select T.RN, T.ID, T.X, case when T.X+CTE.SumX < 0 then 0 else T.X+Cte.sumX end from T
INNER JOIN CTE
on CTE.RN+1=T.RN)
Select * from cte;
.
CTE: ARaw is just a sample data set
CTE: T adds a sequental row number incase there are gaps in the IDs allowing for a more simple joining approach on the recursive CTE.
CTE: CTE is the recursive CTE that keeps a running total and has a case statement to reset the running total to 0 when it falls below 0

Answer 2

You could use a case statement, but that would not be a true running total
with t as (
select 5 as x, 1 as id from dual
union all
select -10, 2 as id from dual
union all
select 20, 3 as id from dual
union all
select 30, 4 as id from dual
union all
select 10, 5 as id from dual
)
select t.x,
case when sum(x) over (order by id) < 0 then 0
else sum(x) over (order by id)
end running_total
from t
order by id;
X RUNNING_TOTAL
5 5
-10 0
20 15
30 45
10 55