How to restrict access to a page?

Try this: is_user_logged_in

function mypage_function() {
  if( is_user_logged_in() ) {
    get_template_part('mypage');
  }else{
    echo 'please login for awesomeness';
  }
}

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)