:new and :old values dynamically in oracle Trigger

Question

I have to track the data changes in a single audit table test_audit which can be used in other triggers to track the changes. I have tried this code but stuck in populating old and new values . Any help on this is much appreciated.

create table test (ID NUMBER , ENAME VARCHAR2(10) , LOCATION VARCHAR2(10));

 create or replace trigger my_trigger
    after update on TEST
    for each row
    declare
       ACTION VARCHAR2(10);
     begin
    
    IF DELETING THEN
          ACTION := 'DELETE';
        ELSIF UPDATING THEN
          ACTION := 'UPDATE';
        END IF;
                 
       for i in (select column_name,table_name from all_tab_columns
                 where table_name = 'TEST'
                 )
       loop
         if updating(i.column_name) then
          INSERT
          INTO TEST_AUDIT
            (
                TABLE_NAME,
                COLUMN_NAME,
                OLD_VALUE,
                NEW_VALUE,
                ACTION,
                UPDATED_BY,
                UPDATED_DT
                        )
            VALUES
            (   
                i.table_name,
                i.column_name,
             --   :old.column_name,--- how to get old and new values?
              --  :new.column_name,---
                ACTION,         
               USER,
               SYSDATE
            );
       end if;
       end loop;
       
    end;

Answer 1

The variables called :new and :old (unless you decide to rename them in the declaration of the trigger) are variables of the rowtype of the table you place the trigger on. So you use :new.<column_name> and :old.<column_name>.