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1.  simplest case
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create table emp (ename varchar2(10),ssn integer);

select * from emp;


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2.  columns are in different tables.
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create table emp (empid integer,ename varchar2(10));
create table emp_part2 (empid integer,ssn integer);

select a.ename,b.ssn
from emp a
    ,emp_part2 b
where a.empid = b.empid
/


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3.  one or even both columns are not actually selected in the result set, but are referenced somewhere in the query.
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create table emp (empid integer,ename varchar2(10));
create table emp_part2 (empid integer,ssn integer);

select a.ename
from emp a
where exists (
               select null
               from emp_part2 b
               where a.empid = b.empid
               and b.ssn = '123456789'
             )
/


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4.  lots of redirection and renaming and hidden predicate action but still, ultimately both columns are referenced.
-------------------------------------------------------------------------------------------------------------------

create table emp (empid integer,ename varchar2(10));
create table emp_part2 (empid integer,ssn integer);

create or replace view emp_v1
as
select ssn employee_socsec,empid
from emp_part2
where ssn like '123%'
/

create or replace view emp_v2
as
select ename employee_name,empid
from emp
/


create synonym my_emp_syn_1 for emp_v1;
create synonym my_emp_syn_2 for my_emp_syn_1;
create synonym mu_emp_syn_3 for my_emp_syn_2;

create synonym my_emp_part_2_syn_1 for emp_v2;
create synonym my_emp_part_2_syn_2 for my_emp_part_2_syn_1;
create synonym my_emp_part_2_syn_3 for my_emp_part_2_syn_2;

select employee_name
from my_emp_part_2_syn_2
where empid in (
                 select empid
                 from my_emp_syn_2
               )
/

orclz>
orclz> exec dbms_fga.add_policy(-
> object_schema=>'scott',-
> object_name=>'emp',-
> policy_name=>'kevpol',-
> audit_column=>'ename,ssn',-
> handler_schema=>'scott',-
> handler_module=>'does_not_exist',-
> statement_types=>'select',-
> audit_column_opts=>dbms_fga.all_columns)

PL/SQL procedure successfully completed.

orclz> select ename from emp;

ENAME
----------
jw

orclz> select ssn from emp;

       SSN
----------
         1

orclz> select * from emp;
select * from emp
              *
ERROR at line 1:
ORA-28144: Failed to execute fine-grained audit handler
ORA-06550: line 1, column 7:
PLS-00201: identifier 'SCOTT.DOES_NOT_EXIST' must be declared
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored


orclz>