php - 在 CodeIgniter 中获取 select 语句的空结果

Question

在这个项目中，大学必须根据两个参数主题和分数来搜索被录取的学生我已经编写了查询，但我得到了空结果

这是搜索候选者的 Controller

public function check_search_students()
     {
      $config = array(
                    array(
                            'field' =>'subject',
                            'label' =>'Subject',
                            'rules' =>'required|trim'
                         ),
                    array(
                            'field' =>'mark',
                            'label' =>'Mark',
                            'rules' =>'is_natural'
                        )
                   );
        $this->form_validation->set_error_delimiters('<font color = "red">','</font>');
        $this->form_validation->set_rules($config);
        if($this->form_validation->run()===False)
        {
                $this->search_students();    // another function
        }
        else
        {
            $collegeid=$this->session->userdata('id');
            $info['name'] = $this->college_model->get_student_name();
            $info['search_student']=$this->college_model->search($collegeid);
            $this->load->view('employer/view_search_students',$info);
        }
     }

示范大学模型

public function search($collegeid)
    {

        $title = $this->input->post('subject');
        $mark = $this->input->post('mark');
        $y=0;
        if($mark==0)
        {
        $query=$this->db->query('SELECT s.name,s.age,p.sub_title ,s.mark 
                                 FROM applied_subs ae, student s, post_subjects p
                                 WHERE ae.college_id=? and  ae.student_id = s.id
                                 AND p.id=ae.sub_id AND p.sub_title = "$title" ',
                                 array($collegeid)
                               );
         return $query->result_array();
        }
       else
        {   
        $query=$this->db->query('SELECT s.name,s.age,p.sub_title ,s.mark 
                                 FROM applied_subs ae, student s, post_subjects p
                                 WHERE ae.college_id=? and  ae.student_id = s.id
                                 AND p.id=ae.sub_id AND p.sub_title = "$title" AND p.mark="$mark"',
                                 array($collegeid)
                               );
        return $query->result_array();
        }
   }

查看--->view_search_students

<table>
         <tr>
         <th> Name </th>
         <th> Mark </th>
    </tr>
         <?php foreach($search_student as $value): ?>
    <tr>
            <td> <?php echo $value['name'] ?> </td>
            <td> <?php echo $value['mark'] ?> </td>
    </tr>
    <?php endforeach ?>
</table>

Answer 1

你搞乱了单引号和双引号。

您需要在 SQL 中的值周围添加单引号，而不是添加双引号。

这就是问题所在。

请检查以下内容:

改变

 if($mark==0)
        {
        $query=$this->db->query('SELECT s.name,s.age,p.sub_title ,s.mark 
                                 FROM applied_subs ae, student s, post_subjects p
                                 WHERE ae.college_id=? and  ae.student_id = s.id
                                 AND p.id=ae.sub_id AND p.sub_title = "$title" ',
                                 array($collegeid)
                               );
         return $query->result_array();
        }
       else
        {   
        $query=$this->db->query('SELECT s.name,s.age,p.sub_title ,s.mark 
                                 FROM applied_subs ae, student s, post_subjects p
                                 WHERE ae.college_id=? and  ae.student_id = s.id
                                 AND p.id=ae.sub_id AND p.sub_title = "$title" AND p.mark="$mark"',
                                 array($collegeid)
                               );
        return $query->result_array();
        }

至

 if($mark==0)
        {
        $query=$this->db->query("SELECT s.name,s.age,p.sub_title ,s.mark 
                                 FROM applied_subs ae, student s, post_subjects p
                                 WHERE ae.college_id=? and  ae.student_id = s.id
                                 AND p.id=ae.sub_id AND p.sub_title = '$title' ",
                                 array($collegeid)
                               );
         return $query->result_array();
        }
       else
        {   
        $query=$this->db->query("SELECT s.name,s.age,p.sub_title ,s.mark 
                                 FROM applied_subs ae, student s, post_subjects p
                                 WHERE ae.college_id=? and  ae.student_id = s.id
                                 AND p.id=ae.sub_id AND p.sub_title = '$title' AND p.mark='$mark'",
                                 array($collegeid)
                               );
        return $query->result_array();
        }