Can't get MySQL JOINs to work right

[thincom2000]

I am trying to write a single query that does the following:

- reads all threads where forumid = $forumid
- reads all posts where threads.firstpostid = postid
- reads all polls where threads.pollid = pollid, but only if a poll exists

I tried:

PHP Code:

SELECT thread.*, post.*, IF(thread.pollid = poll.pollid, poll.*, '')
FROM " . TABLE_PREFIX . "thread, " . TABLE_PREFIX . "post, " . TABLE_PREFIX . "poll"
WHERE thread.forumid = '" . $forumid . "'
    AND post.postid = thread.firstpostid
    AND IF(thread.pollid = poll.pollid, poll.pollid = thread.pollid, '1 > 0')
ORDER BY dateline DESC 


but it just gives T_STRING errors and returns NULL...