如何在codeigniter中获取具有特定ID的最后一条记录

Question

这里有 2 张桌子。第一个是customer，第二个是membership

现在我只想从这些 jioned 表（客户和会员）中获取带有特定 customer_id 的最后一条记录。

这是我的客户表结构

这是我的会员表结构和所需的最新插入行

这里我自己试过一个代码

    $results="";
        $this->db->select('customer.*,membership.*');
        $this->db->from('customer');
        $this->db->join('membership', 'customer.id = membership.customer_id', 'left'); 
       /* $this->db->order_by('membership.id','DESC');
        $this->db->limit('1');*/
        $query = $this->db->get();
        $data = $query->result_array();


$todayDate =  date("d-m-Y"); 
foreach ($data as $value) { 

    $this->db->select('customer.*,membership.*');
        $this->db->from('customer');
        $this->db->join('membership', 'customer.id = membership.customer_id', 'left'); 
        $this->db->where('membership.customer_id', $value['customer_id']);
        $this->db->order_by('membership.customer_id','DESC');

        $this->db->limit('1');
        $query = $this->db->get();
        $dataa = $query->result();

     foreach ($dataa as $values) {

            $date1 = new DateTime($todayDate);
            $date2 = new DateTime($values->end_date);

            $diff=date_diff($date1,$date2);
         $days =  $diff->format("%a"); 
         $pos =  $diff->format("%R");

        if($pos == "+" && $days >= 0){

            $item[] = $values;

        }         

    }

但它返回两个连接表中的所有行。但我只想要每个客户 ID 的最新（最后）行..！

请告诉我哪里出错了。谢谢

Answer 1

要根据最高 id 从会员表中获取每个客户的最后一条记录，您可以通过调整加入部分来自我加入会员，例如

$this->db->select('c.*,m.*');
$this->db->from('customer as c');
$this->db->join('membership as m', 'c.id = m.customer_id', 'left'); 
$this->db->join('membership as m1', 'm.customer_id = m1.customer_id AND m.id < m1.id', 'left'); 
$this->db->where('m1.id IS NULL', null, false)
$query = $this->db->get(); 

普通的 SQL 类似于

SELECT c.*,m.*
FROM customer AS c 
LEFT JOIN membership AS m ON c.id = m.customer_id 
LEFT JOIN membership AS m1 ON m.customer_id = m1.customer_id 
               AND m.id < m1.id
WHERE m1.id IS NULL

Answer 2

改变这个：
$dataa = $query->result();
对此：
$dataa = $query->row();