如果使用了JOIN，有相同的字段名，如何区别？
$list = $this->alias('a')
->join('LEFT JOIN onethink_collect b on a.md5=b.doc_md5 and b.uid ='.$user['id'])
->field('a.*,b.uid,b.doc_md5,b.status as favsta,b.id as favid')
->order('create_time desc')
->limit(6)
->select();
TP框架中ajax U方法不解析
