ThinkPHP中如何实现MySQL多表联查

select t1.*,t2.name as deptname from sp_user as t1,sp_dept as t2 where t1.dept_id = t2.id;

select t1.*,t2.name as deptname from sp_user as t1 left join sp_dept as t2 on t1.dept_id = t2.id;

    //多表联查(table)
    public function test18() {
        //实例化模型
        $model = M();
        //查询
        $result =$model->field('t1.*, t2.name as deptname')->table('sp_user as t1, sp_dept as t2')
　　　　　　　　　　　　 ->where('t1.dept_id = t2.id')->select();
        dump($result);
    }
    //多表联查(join)
    public function test19() {
        //实例化模型
        $model = M('User');
        //查询
        $result = $model->field('t1.*, t2.name as deptname')->alias('t1')
　　　　　　　　　　　　 ->join('left join sp_dept as t2 on t1.dept_id = t2.id')->select();
        dump($result);
    }