Creating Audit Data with Triggers

Question

I want to create an audit table like
AuditTable(
FieldName Varchar2(40),
OldValue Varchar2(100),
NewValue Varchar2(100),
User varchar2(20),
UpdtDate Date)
Whenever Table X is updated, then the Trigger should capture the changes and create a row for each field in the UPdate Statement.
I don't want to turn on Audit as the DB is very big and high transaction oriented. I just want to watch a particulare table only.
I need a little guidance in parsing the update statement and get the fieldnames, their old values and new values.

Answer 1

Well, you could certainly audit a single table - you don't have to audit every table.
In any case, the trigger would look something like:
create or replace trigger t_audit
after update on t
for each row
begin
  if updating('column_a') then
    insert into audittable values ('column_a', :old.column_a, :new.column_a, user, sysdate);
  end if;
  ... repeat for all columns
  if updating('column_z') then
    insert into audittable values ('column_z', :old.column_z, :new.column_z, user, sysdate);
  end if;
end;You can use the data dictionary (user_tab_columns) to automate the writing of that trigger if there are many columns.