"EMP" table(If it has the following columns)
emp_name
username

select emp_name 
from emp 
where upper(username) = :APP_USER

function CUSTOMAUTHENTICATION
(p_username in VARCHAR2,
p_password in VARCHAR2)
return BOOLEAN
is
  v_cnt pls_integer := 0;
  v_emp  varchar2(100); 
begin
  
 SELECT 1 INTO v_cnt 
              FROM app_user
            WHERE UPPER (username) = UPPER (p_username)
     AND PASSWORD = get_hash (p_username, p_password);
  
  select emp_name into v_emp
      from users1 where UPPER(username)= UPPER(p_username); 
 
  
   APEX_UTIL.SET_SESSION_STATE('FUSER',UPPER(v_emp)); 
    RETURN TRUE;
APEX_UTIL.SET_SESSION_STATE('FUSER');

     RETURN FALSE;
 
end CUSTOMAUTHENTICATION;