mysql 利用left join 查询出有重复的字段时，应该怎么办？

SELECT tp_vote_item.*,tp_zpclass.zpclassname from tp_vote_item  LEFT JOIN  tp_zpclass on tp_vote_item.zpclassid=tp_zpclass.id where tp_vote_item.id=6

　　利用tp3.2 的语法是：

$tiaojian['tp_vote_item.id'] = $zid;

$res= M('Vote_item')->join(' LEFT JOIN  tp_zpclass on tp_vote_item.zpclassid=tp_zpclass.id')->where($tiaojian)->field('tp_vote_item.*,tp_zpclass.zpclassname')->find();