尝试从 2 个表 codeigniter 中获取数据时出错

Question

我必须从 2 个表中获取数据。我的表是“Study”、“Users”和“Subjects”

"Study" includes:(id, user_id[is the foreign key to the column "id" of the table "Users"], subject_id[is the foreign key to the column "id" of the table "Subjects"], grade, date)

"Users" includes:(id,username,name,lastname,password,type,status,date)

"Subjects" includes:(id, career_id, name, description, hours)

我想在最后得到这样的东西：

我遇到了这个错误：

这是我的代码：我的视图文件（“主页”）：

    <html>

    <head>
        


    </head>

<body>

    <div class="container"> 
    <div class="row">
    <div class="col-md-12">

        <h2 align="center">TABLE:Study</h2>
        
        <input id="busqueda_tabla" type="text">
            <table class="table table-hover" align="center" border="1" cellspacing="0" cellpadding="0" width="700" id="tabla_busqueda">
                <thead>
                    <th>id</th>
                    <th>User</th>
                    <th>Subject</th>
                    <th>Grade</th>
                    <th>Date</th>
                    <th>Action</th>
                </thead>

<tbody>
    <?php

    if (count($records) > 0 && $records != false) {
        foreach($records as $record) {
            
            echo "<tr>
                      <td>".$record['id']."</td>
                      <td>".$record['user']."</td>
                      <td>".$record['subject']."</td>
                      <td>".$record['grade']."</td>
                      <td>".$record['date']."</td>
                      <td align='center'>
                         
                         <button type='button' class='btn btn-primary'>EDITAR</button></a> |
                    
                         <button type='button' class='btn btn-danger'>BORRAR</button></a>

                  </tr>";
        }

       }
    ?>

</tbody>

    </table>

        </div>
        </div>
        </div>

</body>
</html>

这是我的控制器文件（“主页”）：

    <?php

    class Home extends CI_Controller{

         public function __construct(){
             parent::__construct();

             $this->load->model("Crudmodel");

        }


        public function index(){

    # get all data in Study table
    $selectStudys = $this->Crudmodel->selectStudys();

    foreach ($selectStudys as $key => $study) 
    {
        # get UserNames
        $user = $this->Crudmodel->getName($study['user_id']);

        #get Subject Names
        $subject = $this->Crudmodel->getSubName($study['subject_id']);


        #append both NEW VALUES to same array


        $data[$key]['user_id'] = $user[0]['username'];
        $data[$key]['subject_id'] = $subject[0]['name'];

    }


    $data['records'] = $selectStudys;
    $this->load->view('home', $data);

}



   }
    
?>

还有我的模型文件（“Crudmodel”）：

  <?php

    class Crudmodel extends CI_Model{

        public function __construct(){
         parent::__construct();

         $this->load->database();

        }


        function selectStudys()
{
    $query= $this->db->query("SELECT * FROM Study");
    $result = $query->result_array();
    return $result;
}

function getName($name)
{
    $query= $this->db->query("SELECT username FROM Users WHERE id = $name ");
    $result = $query->result_array();
    return $result;
}

function getSubName($subject)
{
    $query= $this->db->query("SELECT name FROM Subjects WHERE id = $subject ");
    $result = $query->result_array();
    return $result;
}








}
?>

希望你能帮助我:/

Answer 1

Undefined indexes 和 trying to get 属性 non-object 或多或少意味着同一件事，即你没有得到正确的数据，或者你试图获取的变量或索引未初始化或未定义，并且造成这种情况的原因可能是查询中的错误或空白数据 return 通过查询您是运行。

我想请求你像这样提取你的查询数据

$check = $this->db->query("SELECT * FROM SOMETHING AND YOUR CONDITION AND STUFF HERE"); 

if($check->num_rows()>0){
 $result = $check->result(); 
 return $result;
}else{
 return false; // or anything you want. 
}

假设这个查询函数存储在模型中，而你正在这样调用你的模型

$someVariable = $this->model_name->function();
if($someVariable!==FALSE){
// handle
}else 
{
// handle
}

最后，不知道为什么，但有时我也会反驳双引号的问题，是的，我知道..双引号内的变量起作用，我只是说有时......至少它发生在我身上，所以我想请求最后一件事。尝试像这样调试您的查询，目前您有

"SELECT * FROM TABLE WHERE THIS = $THAT"

将此更改为

"SELECT * FROM TABLE WHERE THIS = '".$THAT."'"

希望对您有所帮助！

已编辑： （抱歉，我未能展示您自己代码中的示例）您的模型文件

  <?php

    class Crudmodel extends CI_Model{

        public function __construct(){
         parent::__construct();

         $this->load->database();

        }


        function selectStudys()
{
    $query= $this->db->query("SELECT * FROM Study");
    if($query->num_rows()>0){
       $result = $query->result_array();
     }else{
      $result = "";
          // or anything you can use as error handler
      return $result;
    }
}

function getName($name)
{
    $query= $this->db->query("SELECT username FROM Users WHERE id = $name ");
    if($query->num_rows()>0){
    $result = $query->result_array();
    }else{
    $result = "";
          // or anything you can use as error handler
    return $result;
  }
}

function getSubName($subject)
{
    $query= $this->db->query("SELECT name FROM Subjects WHERE id = $subject ");
  if($query->num_rows()>0){
     $result = $query->result_array();
  }else{
      $result = "";
          // or anything you can use as error handler
      return $result;
}
    }

 function CombineResults($subject, $name){
  // you can also use this
   $query = $this->db->query("SELECT sub.name, user.username FROM Subjects sub, Users user WHERE sub.id=$subject AND user.id = $name");
   if($query->num_rows()>0){
        return $query->result();
         }else{
           return "";
              // or anything you can use as error handler
        }
    }       
  }
    ?>

你的控制器文件

  public function index(){

    # get all data in Study table
    $selectStudys = $this->Crudmodel->selectStudys();
    // we have condition on this model method/function we can validate
    // response comming from this method and add handler just like we did
    // for queries. your main problem can be this

    foreach ($selectStudys as $key => $study) 
    {
        # get UserNames
        $user = $this->Crudmodel->getName($study['user_id']);

        #get Subject Names
        $subject = $this->Crudmodel->getSubName($study['subject_id']);


        #append both NEW VALUES to same array

        if(!empty($user[0]['username'])){
        $data[$key]['user_id'] = $user[0]['username'];
        // your main problem can be this. may be it is not getting value from query this is why we have put validation on model function and error handler condition here
        }else{
         $data[$key]['user_id'] = ''; // or anything as your else condition you can use as error handler 
        }
        if(!empty($subject[0]['name'])){
        $data[$key]['subject_id'] = $subject[0]['name'];
        // your main problem can be this. may be it is not getting value from query this is why we have put validation on model function and error handler condition here
        }else{
           $data[$key]["subject_id"] = "";
          // or anything you can use as error handler
        }

    }


    $data['records'] = $selectStudys;
    $this->load->view('home', $data);

}

Answer 2

我已将您的查询更改为加入查询，只需将您的代码更改为以下内容

public function index(){

    # get all data in Study table

    $query = $this->db->query("SELECT sd.user_id as id,sd.grade as grade,sd.date as date,sd.subject_id as subject,ur.username as user FROM Study as sd,Users as ur,Subjects as sb WHERE ur.id=sd.user_id and sb.id=sd.subject_id");

    $result = $query->result_array();

    $data['records'] = $result;

    $this->load->view('home', $data);

}

现在运行代码

尝试从 2 个表 codeigniter 中获取数据时出错

Error trying to fetch data from 2 tables codeigniter

php

mysql

codeigniter

fetch