左链接、右链接

//Left Join   
$Blog->table('comment a')->join('reply b on a.id=b.cid')->field('a.*,b.*')->order('id desc')->limit('8')->findall();   
  
//Right Join   
$Blog->table('comment a')->join(array('right','reply b on a.id=b.cid'))->field('a.*,b.*')->order('id desc')->limit('8')->findall();