日期顺序由DESC和'header_id'分组在CodeIgniter查询中

I need a query, receive_date descending order also have header_id group by from table messages. Where join message_headers table status = 0.

    $this->db->select('me.*, mh.*,max(me.receive_date) as receive_date');
    $this->db->from('messages as me');
    $this->db->join('message_headers as mh', 'em.header_id = eh.id');
    $this->db->where('me.account_id',1); 
    $this->db->where('mh.status', 0);
    $this->db->order_by('receive_date', 'DESC');
    $this->db->group_by('me.header_id');
    $message = $this->db->get()->result_array();

output not show desc order. some broke down. some right way.

$this->db->select('me.*, mh.*,max(me.receive_date) as receive_date');
$this->db->from('messages as me');
$this->db->join('message_headers as mh', 'me.header_id = mh.id');
$this->db->where('me.account_id',1); 
$this->db->where('mh.status', 0);
$this->db->group_by('me.header_id');
$this->db->order_by('receive_date', 'DESC');
$message = $this->db->get()->result_array();

Use STR_TO_DATE for date format.

$this->db->select('me.*, mh.*, MAX(STR_TO_DATE(me.receive_date, '%Y-%m-%d %h:%i:%s')) as receive_date');
$this->db->from('messages as me');
$this->db->join('message_headers as mh', 'em.header_id = eh.id');
$this->db->where('me.account_id',1); 
$this->db->where('mh.status', 0);
$this->db->order_by('receive_date', 'DESC');
$this->db->group_by('me.header_id');
$message = $this->db->get()->result_array();