declare
  l_alert number;
  l_it_exists varchar2(1);
begin
  select null
    into l_it_exists
    from password_table p
    where p.user_name     = :user_logon.user_name
      and p.user_password = :user_logon.user_password;

  go_block('dept');
  	    
exception
  when no_data_found then
    l_alert := show_alert('alert');
end;