You must convert the data type of a column if its type will cause Oracle Data Mining to interpret it incorrectly. For example, zip codes identify different postal zones; they do not imply order. If the zip codes are stored in a numeric column, they will be interpreted as a numerical attribute. You must convert the data type so that the column data can be used as a categorical attribute by the model. You can do this using the TO_CHAR function to convert the digits 1-9 and the LPAD function to retain the leading 0, if there is one.
LPAD(TO_CHAR(ZIPCODE),5,'0')