CREATE OR REPLACE FUNCTION getuser 
RETURN user_users.username%TYPE IS
-- explain use of %TYPE
vOSUser user_users.username%TYPE;
-- explain INTO and return
BEGIN
  SELECT osuser
  INTO vUser
  FROM gv$session
  WHERE sid = (
    SELECT sid
    FROM gv$mystat
    WHERE ROWNUM = 1);
 
  RETURN vuser; 
EXCEPTION
  WHEN OTHERS THEN
    RETURN 'UNK'; 
END getuser;
/
 
-- test getuser function
SELECT getuser FROM dual;
 
Simple FUNCTION Used IN An INSERT Statement 
 
CREATE TABLE my_table (
col_values   VARCHAR2(10),
insert_by    VARCHAR2(30));
 
INSERT INTO my_stuff VALUES ('ABC', getosuser);
INSERT INTO my_stuff VALUES ('ABCD', 'Harold Stassen');
INSERT INTO my_stuff VALUES ('ABCDE', getosuser);
INSERT INTO my_stuff VALUES ('ABCDEF', 'Mary Lamb');
INSERT INTO my_stuff VALUES ('AB', getosuser);
COMMIT;
 
SELECT * FROM my_table;