Sql codeigniter数据表联接查询不工作

//我正在CI中使用数据库，但运行不正常。请查看连接查询并建议如何持续连接条件

 private function _get_datatables_query($term='')
 {
  $user_id = $this->session->userdata("user_id");
  $user_type = $this->session->userdata("user_type");  
     $column =           array('A.type','C.school_name','A.mobile','A.email','A.birthdate','A.anniversary','A.gender','A.firstname','A.lastname');
      $this->db->select('A.type,C.school_name,A.mobile,A.email,A.birthdate,A.anniversary,A.gender,A.firstname,A.lastname,C.s2m_admin_id,A.status,A.id,A.pusername');
      $this->db->from('users as A');
      $this->db->join('school_user as B', 'B.user_id = A.id');
      $this->db->join('school as C', 'C.id = B.school_id');
      $this->db->join('school as D', 'D.s2m_admin_id = A.id');//<= i am having problem in this line else is working properly .if i add this line query return nothing.
      $this->db->having('A.status','active'); 

      $this->db->like('A.type', $term);
       $this->db->or_like('A.mobile', $term);
      $this->db->or_like('A.firstname', $term);

private函数\u get\u datatables\u查询（$term=''）
{
$user\u id=$this->session->userdata（“user\u id”）；
$user\u type=$this->session->userdata（“user\u type”）；
$column=array（'A.type'，'C.school\u name'，'A.mobile'，'A.email'，'A.birthdate'，'A.周年纪念'，'A.gender'，'A.firstname'，'A.lastname'）；
$this->db->select（'A.type，C.school\u name，A.mobile，A.email，A.birthdate，A.周年纪念日，A.gender，A.firstname，A.lastname，C.s2m\u admin\u id，A.status，A.id，A.pusername'）；
$this->db->from（'users as A'）；
$this->db->join（'school\u user as B'，'B.user\u id=A.id'）；
$this->db->join（'school as C'，'C.id=B.school_id'）；
$this->db->join（'school as D'，'D.s2m_admin_id=A.id'）；//db->having（'A.status'，'active'）；
$this->db->like（'A.type'，$term）；
$this->db->或类似（'A.mobile'，$term）；
$this->db->或类似（'A.firstname'，$term）；

试试这个

$user_id = $this->session->userdata("user_id");
$user_type = $this->session->userdata("user_type");  
//$column =  array('U.type','S.school_name','U.mobile','U.email','U.birthdate','U.anniversary','U.gender','U.firstname','U.lastname');
$this->db->select(*);
$this->db->from('users as U');
$this->db->join('school_user as SU', 'SU.user_id = U.id');

# added where clause
$this->db->where('school.id = SU.school_id OR school.s2m_admin_id = U.id');

$this->db->having('U.status','active'); 

$this->db->like('U.type', $term);
$this->db->or_like('U.mobile', $term);
$this->db->or_like('U.firstname', $term);

---

我不知道你到底想做什么，但试一下$this->db->join（'school as D'，'D.s2m_admin_id=A.id'，'left'）；