external tables with decode function

Hi,

I have created the following external table without a decode function as it is not supported. And that, I am using the decode function in the select statement to read the table, but it is failing with the below error.   Please let me know if my decode statement is correct or not. And also, please calrify me if we can use decode function in the select statement to read the external table. 

Your help is really appreciated.

DDL:

CREATE TABLE xtern_OCT._IC011D_11.  (
COMPANY_NUMBER             VARCHAR2(03),
AGENCY_NUMBER              VARCHAR2(06),
LINE_OF_BUSINESS           VARCHAR2(02),
UNIT_NUMBER                VARCHAR2(04),
POLICY_NUMBER              VARCHAR2(10),