The idea is that each account has a balance. Say I have a checking and savings account: there's one row for each and the bank will kindly let either of them get a negative balance provided the sum of both balances is positive.
You may not care for this schema design, but I think most people would be surprised that Oracle silently corrupts data and violates constraints here.
You may not care for this schema design, but I think most people would be surprised that Oracle silently corrupts data and violates constraints here.