Спасибо за все ваши ответы, на основе ваших ответов, наконец, я выполнил требование с помощью следующего кода:
create or replace TRIGGER ACTIVITY_LABEL_TRIGGER
AFTER UPDATE OF ACTIVITY_LABEL, NOTES
ON OPS_BUILD_ACTIVITY_LABEL
FOR EACH ROW
BEGIN
if ( nvl(:OLD.ACTIVITY_LABEL,'xYz#@!') != nvl(:NEW.ACTIVITY_LABEL,'xYz#@!')) then
INSERT INTO ACTIVITY_LABEL_AUDIT_LOG
(TABLE_NAME,
COLUMN_NAME,
OLD_VALUE,
NEW_VALUE,
UPDATED_BY,
UPDATED_DTM)
VALUES
('OPS_BUILD_ACTIVITY_LABEL',
'ACTIVITY_LABEL',
:OLD.ACTIVITY_LABEL,
:NEW.ACTIVITY_LABEL,
:NEW.LAST_UPDATED_BY,
:NEW.LAST_UPDATED_DTM);
end if;
if (nvl(:OLD.NOTES,'xYz#@!') != nvl(:NEW.NOTES,'xYz#@!') ) then
INSERT INTO ACTIVITY_LABEL_AUDIT_LOG
(TABLE_NAME,
COLUMN_NAME,
OLD_VALUE,
NEW_VALUE,
UPDATED_BY,
UPDATED_DTM)
VALUES
('OPS_BUILD_ACTIVITY_LABEL',
'NOTES',
:OLD.NOTES,
:NEW.NOTES,
:NEW.LAST_UPDATED_BY,
:NEW.LAST_UPDATED_DTM);
end if;
END;