Can I divide an amount across multiple parties and round to the 'primary' party in a single SQL query? - sql

Question

I am working on an oracle PL/SQL process which divides a single monetary amount across multiple involved parties in a particular group. Assuming 'pGroupRef' is an input parameter, the current implementation first designates a 'primary' involved party, and then it splits the amount across all the secondaries as follows:
INSERT INTO ActualValue
SELECT
...
pGroupRef AS GroupRef,
ROUND(Am.Amount * P.SplitPercentage / 100, 2) AS Amount,
...
FROM
Amount Am,
Party P
WHERE
Am.GroupRef = pGroupRef
AND P.GroupRef = Am.GroupRef
...
P.PrimaryInd = 0;
Finally, it runs a second procedure to insert whatever amount is left over to the primary party, i.e.:
INSERT INTO ActualValue
SELECT
...
pGroupRef AS GroupRef,
Am.Amount - S.SecondaryAmounts,
FROM
Amount Am,
Party P,
(SELECT SUM(Amount) AS SecondaryAmounts FROM ActualValue WHERE GroupRef = pGroupRef) S
WHERE
Am.GroupRef = pGroupRef
AND P.GroupRef = Am.GroupRef
...
P.PrimaryInd = 1;
However, the full query here is very large and I am making this area more complex by adding subgroups, each of which will have their own primary member, and the possibility of overrides - hence if I continued to use this implementation then it would mean a lot of duplicated SQL.
I suppose I could always calculate the correct amounts into an array before running a single unified insert - but I feel like there has to be an elegant mathematical way to capture this logic in a single SQL Query.

Answer 1

So you can use analytical functions to get what you are looking for. As I didn't know your exact structure, this is only an example:
SELECT s.party_id, s.member_id,
s.portion + DECODE(s.prime, 1, s.total - SUM(s.portion) OVER (PARTITION BY s.party_id),0)
FROM (SELECT p.party_id, p.member_id,
ROUND(a.amt*(p.split/100), 2) AS PORTION,
a.amt AS TOTAL, p.prime
FROM party p
INNER JOIN amount a ON p.party_id = a.party_id) s
So in the query you have a subquery that gathers the required information, then the outer query puts everything together, only applying the remainder to the record marked as prime.
Here is a DBFiddle showing how this works (LINK)
N.B.: Interestingly in the example in the DBFiddle, there is a 0.01 overpayment, so the primary actually pays less.