php - 如何从 codeigniter 中的三个表中检索数据以获得完整 View

Question

我是 codeigniter 和 php 的新手。我的DB 中有两个表，我需要做的是从表user_details、user_comments 中检索数据。

user_details 的

id 与 user_comments 中的 id_user 相同。

我想在我的 View 中显示一些输出，因为没有条件，我需要所有用户列表，其中包含 first_name，last_name from user_details 和 number of comment by user from comm_id.

        public function user_details(){

        $query=$this->db->select('id, f_name, l_name')
                ->from('user_details');

            $array=array();

            foreach($query->result() as $row)
                 {
                    $id=$row->id;
                    $array['f_name']=$row->f_name;
                    $array['l_name']=$row->l_name;
                    $query1=$this->db->select('comments')
                    ->from('user_comments')
                    ->where('id_user',$id);
                    foreach($query1->result() as $row1){

                            $array['comments'] = COUNT($row->comments;


                    }


                 }


            return $array;


    }

我需要帮助请帮助我...

Answer 1

您不想运行 N+1 个查询。您可以通过查询一次获取所有必要的数据

SELECT u.id, u.f_name, u.l_name, COUNT(c.id_user) comments_count
  FROM user_details u LEFT JOIN user_comments c
    ON u.id = c.id_user
 GROUP BY u.id, u.f_name, u.l_name

示例输出:

| id | f_name | l_name | comments_count |
|----|--------|--------|----------------|
|  1 |   John |    Doe |              4 |
|  2 |   Jane |    Doe |              2 |

Here is a SQLFiddle demo

Recommended reading:

• A Visual Explanation of SQL Joins

---

In Codeigniter this translates to something along the lines of

public function user_details() 
{
    $rows = $this->db
        ->select('u.id', 'u.f_name', 'u.l_name')
        ->select('COUNT(c.id_user) AS comments_count', FALSE)
        ->from('user_details AS u')
        ->join('user_comments AS c', 'u.id = c.id_user', 'left')
        ->group_by('u.id', 'u.f_name', 'u.l_name')
        ->get()
        ->result_array();

    return $rows;
}