You can specify the decimal separator, with the TO_NUMBER function within a query. Without having to alter the session or configure the parameter in the system.

SELECT TO_NUMBER('-AusDollars100','L9G999D99',
' NLS_NUMERIC_CHARACTERS = '',.''
NLS_CURRENCY = ''AusDollars''
') "Amount"
FROM DUAL;


This way it does not work for me.