sql pocitani bodygardu

<?php
$sql_w = "
SELECT SUM(items_cnt) AS items_sum
 FROM (
  (
   SELECT b.user_id, SUM(b.einheiten) AS items_cnt
    FROM users_personal_b AS b
    WHERE b.user_id=".$user_id."
  )
  UNION (
   SELECT k.user_id, SUM(k.einheiten) AS items_cnt
    FROM users_personal_k AS k
    WHERE k.user_id=".$user_id."
   )
  ) AS i
";
?>

CREATE TABLE IF NOT EXISTS `users_personal_b` (
  `user_id` int(11) NOT NULL,
  `personal_id` int(11) NOT NULL,
  `einheiten` int(100) NOT NULL DEFAULT '0'
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;


INSERT INTO `users_personal_b` (`user_id`, `personal_id`, `einheiten`) VALUES
(1, 1, 0),
(1, 3, 10);

CREATE TABLE IF NOT EXISTS `users_personal_k` (
  `user_id` int(11) NOT NULL,
  `personal_id` int(11) NOT NULL,
  `einheiten` int(100) NOT NULL DEFAULT '0'
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

Column 'user_id' cannot be null