Есть запрос

SELECT c.userid, u.email, u.name, u.username, count(c.userid) AS cnt , sum(c.isgood) as isgood,
 sum(c.ispoor) as ispoor, sum( c.ispoor ) AS ispoor, (sum( c.isgood ) - sum( c.ispoor )) AS votes 
FROM jos_jcomments AS c
JOIN jos_users AS u 
ON u.id = c.userid 
WHERE c.published = 1
   AND c.date >= '2012-05-14 00:00:00' 
   AND c.userid NOT IN('62', '120') 
UNION ALL 
SELECT c.userid, c.email, c.name, c.username , count(c.userid) AS cnt , sum(c.isgood) as isgood, 
sum(c.ispoor) as ispoor, sum( c.ispoor ) AS ispoor, (sum( c.isgood ) - sum( c.ispoor )) AS votes 
FROM jos_jcomments AS c 
WHERE c.published = 1 
   AND c.date >= '2012-05-14 00:00:00' 
   AND c.name <> ''
   AND c.userid = 0

Смысл в чем. Если нет ни одной записи в первом запросе, то получаем ошибку "userid cannon be null". По отдельности все прекрасно работает. Это что? Баг? Или я чего то не понимаю?

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