pl sql trigger determine if insert or update or delete

1CREATE OR REPLACE TRIGGER Audit_emp
2   AFTER INSERT OR UPDATE OR DELETE ON Emp_tab
3   FOR EACH ROW
4   DECLARE
5      Time_now DATE;
6      Terminal CHAR(10);
7   BEGIN
8      -- get current time, and the terminal of the user:
9      Time_now := SYSDATE;
10      Terminal := USERENV('TERMINAL');
11      -- record new employee primary key
12      IF INSERTING THEN 
13         INSERT INTO Audit_table
14            VALUES (Audit_seq.NEXTVAL, User, Time_now,
15               Terminal, 'Emp_tab', 'INSERT', :new.Empno);
16   -- record primary key of the deleted row:
17      ELSIF DELETING THEN                           
18         INSERT INTO Audit_table
19            VALUES (Audit_seq.NEXTVAL, User, Time_now,
20               Terminal, 'Emp_tab', 'DELETE', :old.Empno);
21   -- for updates, record the primary key
22   -- of the row being updated:
23      ELSE 
24         INSERT INTO Audit_table
25            VALUES (audit_seq.NEXTVAL, User, Time_now,
26               Terminal, 'Emp_tab', 'UPDATE', :old.Empno);
27      -- and for SAL and DEPTNO, record old and new values:
28         IF UPDATING ('SAL') THEN
29            INSERT INTO Audit_table_values
30               VALUES (Audit_seq.CURRVAL, 'SAL',
31                  :old.Sal, :new.Sal);
32
33         ELSIF UPDATING ('DEPTNO') THEN
34            INSERT INTO Audit_table_values
35               VALUES (Audit_seq.CURRVAL, 'DEPTNO',
36                  :old.Deptno, :new.DEPTNO);
37         END IF;
38      END IF;
39END;