如何在Codeigniter Active Records中使用'DISTINCT'？

Question

我有一个使用活动记录的查询.

$this->db->select('reg.users_id,reg.registration_id,reg.device_type');
$this->db->join('users as usr','usr.users_id = reg.users_id','left');
$this->db->where('usr.users_status',1);
$this->db->where('reg.users_id',91);
$query = $this->db->get('users_gcm_registration as reg');

我想要取DISTINCT(registration_id).

我怎样才能做到这一点？

Answer 1

你可以使用distinct作为

$this->db->distinct('reg.registration_id');
$this->db->select('reg.users_id,reg.device_type');
....

但更好用 group_by

$this->db->select('reg.users_id,reg.registration_id,reg.device_type');
$this->db->join('users as usr','usr.users_id = reg.users_id','left');
$this->db->where('usr.users_status',1);
$this->db->where('reg.users_id',91);
$this->db->group_by('reg.registration_id');// add group_by
$query = $this->db->get('users_gcm_registration as reg');