Aggregating values in SQL - sql

Question

Im trying to aggregate output values of a customer's bankruptcy in terms of yes (Y), no (N) or no data (N/D) using a window function in a subquery below. For example, if there arise edge cases when in one record the Customer is classified as not bankrupt (N) but in another record on the same CDate it is also classified as no data (N/D), I should get a final aggregated output value as N/D, but it gives me N instead, because of what I've done here by partitioning the customer records over IsBankrupt ascending (asc). The logic behind it which is supposed to be implemented:
Y and Y = Y;
Y and N = Y;
N and N = N;
Y and N/D = Y;
N and N/D = N/D
with sample as (
select date('2020-12-32') as CDate, 123 as CustomerID, 'N/D' as IsBankrupt
union all
select date('2020-12-32') as CDate, 123 as CustomerID, 'N' as IsBankrupt)
select CDate, CustomerID, IsBankrupt, case when CustomerID = 123 then 'N/D' end as ExpectedResult
from
(
select CDate, CustomerID, IsBankrupt,
row_number() over (partition by CustomerID, CDate order by IsBankrupt asc) as flag
from sample
) from subsample
where flag = 1
output:
CDate
CustomerID
IsBankrupt
ExpectedOutput
2020-12-31
123
N
N/D
All the other cases of the previously mentioned logic work. So Question is - how could i update my row_number() over partition by clause so that the logic doesnt break down?

Answer 1

I would suggest aggregation:
select cdate, customerid,
(case when sum(case when IsBankrupt = 'Y' then 1 else 0 end) > 0
then 'Y'
when sum(case when IsBankrupt = 'N/D' then 1 else 0 end) > 0
then 'N/D'
else 'N'
end) as new_flag
from t
group by cdate, customerid;
If you don't like the nested case expressions, you can actually do this based on the ordering of the values:
select cdate, customerid,
max(IsBankrupt) as new_flag
from t
group by cdate, customerid;