Finding the MIN value from the SUM of multiple row grouped by some id - sql

Question

I am using SQLplus connecting to oracle database 12c
I have two tables, Customer and Account, where customers can have multiple accounts (one customer id, but multiple account types). I am trying to get the information on the customer with the largest amount of debt. Suppose we have the following information:
Customer table:
BSB# Customer# Name Address
------------------------------
0123 123456 Adam ABC st
0234 234566 Dave CBC rd
0345 345667 Max DSE st
Account table:
BSB# Customer# Type Balance
---------------------------------
0123 123456 Saving -2300
0123 123456 Credit -500
0123 123456 iSaver 200
0234 234566 Saving 5000
0345 345667 Credit -1500
0345 345667 iSaver -200
The desired output:
Customer# Name Address
-------------------------
123456 Adam ABC St
I can print out the sum of everyone's account balance, but I am not sure how to print out just the information on the account with the lowest accumulated balance. I tried using MIN(SUM(A.Balance)) but I keep getting the error saying "not a single-group function". I wouldn't be surprised if I made a mistake somewhere.
I am relatively new to sql and this is what I have so far. Any advice or pointers would be nice...
SELECT C.Customer#, C.Name, Address, SUM(A.Balance)
FROM Customer C
RIGHT OUTER JOIN Account A
ON C.BSB# = A.BSB#
AND
C.Customer# = A.Customer#
GROUP BY C.Customer#, C.Name, Address;
Thanks!

Answer 1

The following will order the customers by the sum of the balances:
SELECT C.Customer#, C.Name, Address, SUM(A.Balance)
FROM Customer C JOIN
Account A
ON C.BSB# = A.BSB# AND
C.Customer# = A.Customer#
GROUP BY C.Customer#, C.Name, Address
ORDER BY SUM(A.Balance);
If you want only one row, then that depends on the database. Here are some methods:
Change the select to:
SELECT TOP 1 . . .
Add a limit clause to the end of the query:
LIMIT 1
Add a fetch clause to the end of the query:
FETCH FIRST 1 ROWS ONLY
And in Oracle, you can do this with a subquery:
SELECT *
FROM (SELECT C.Customer#, C.Name, Address, SUM(A.Balance)
FROM Customer C JOIN
Account A
ON C.BSB# = A.BSB# AND
C.Customer# = A.Customer#
GROUP BY C.Customer#, C.Name, Address
ORDER BY SUM(A.Balance)
) t
WHERE rownum = 1;

Answer 2

U can use the folowing statement
with MinAccounts as
(
SELECT BSB#, Customer#, Balance
FROM (
SELECT BSB#, t.Customer# , sum(t.Balance) Balance, min(sum(t.Balance)) over () minBalance
FROM Account t
GROUP BY BSB#, Customer#
) d
WHERE Balance = minBalance)
SELECT *
FROM MinAccounts a
JOIN Customer c ON a.BSB# = c.BSB#