NiZZo_ adlı üyeden alıntı: mesajı görüntüle
username ikisindede aynı olduğu için tekrarlaması normal.
Group by yada distinc ile dene bakalım.

SELECT p.id as 'pollsID',c.id as 'contentID', c.title as 'contentTitle',p.title as 'pollsTitle' FROM forum_content as c INNER JOIN forum_polls  as p ON c.username=p.username WHERE c.username='{$user->username}' GROUP BY p.id,c.id
Olmazsa şunu dene.
SELECT content.*,polls.* FROM (c.id as 'contentID', c.title as 'contentTitle',c.username FROM forum_content as c WHERE c.username='{$user->username}') as content INNER JOIN (SELECT p.id as 'pollsID',p.title as 'pollsTitle',p.username FROM forum_polls as p WHERE p.username='{$user->username}') as polls ON content.username=polls.username
İlk sorgu yine tekrarlıyor. İkinci sorgu ise hata veriyor. DISTINC ve GROUP BY seçeneklerini bende denedim. Sonuç şöyle:

Array
(
    [0] => Array
        (
            [pollsID] => 1
            [contentID] => 7
            [contentTitle] => Tanışalım
            [pollsTitle] => Yeni Sitemiz
        )

    [1] => Array
        (
            [pollsID] => 1
            [contentID] => 169
            [contentTitle] => Video istek
            [pollsTitle] => Yeni Sitemiz
        )

    [2] => Array
        (
            [pollsID] => 1
            [contentID] => 170
            [contentTitle] => Program İstek
            [pollsTitle] => Yeni Sitemiz
        )

    [3] => Array
        (
            [pollsID] => 1
            [contentID] => 171
            [contentTitle] => Oyun İstek
            [pollsTitle] => Yeni Sitemiz
        )

)


Type: Array
Last Query [17]: SELECT p.id as 'pollsID',c.id as 'contentID', c.title as 'contentTitle',p.title as 'pollsTitle' FROM forum_content as c INNER JOIN forum_polls  as p ON c.username=p.username WHERE c.username='Administrator' GROUP BY p.id,c.id
Last Function Call: $db->query("SELECT p.id as 'pollsID',c.id as 'contentID', c.title as 'contentTitle',p.title as 'pollsTitle' FROM forum_content as c INNER JOIN forum_polls  as p ON c.username=p.username WHERE c.username='Administrator' GROUP BY p.id,c.id")
Last Rows Returned: 4
İkinci sorgunun hatası:

Warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''contentID', c.title as 'contentTitle',c.username FROM forum_content as c WHERE '