$map['a.username'] = $username;
$map['b.company'] = $company;
/* 获取用户数据 */
$user = M('UcenterMember a')->join('INNER JOIN __COMPANY__ b ON a.id = b.uid')->where($map)->find();

报错：
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'b.company' in 'where clause'
申明：以上字段均存在，company是b表里面的字段，$map里面加a表都正常