尝试从 2 个表 codeigniter 获取数据时出错答案

【问题标题】：Error trying to fetch data from 2 tables codeigniter尝试从 2 个表 codeigniter 获取数据时出错
【发布时间】：2017-04-05 14:00:04
【问题描述】：

我要从 2 个表中获取数据。我的表是“Study”、“Users”和“Subjects”

“学习”包括：(id,user_id[是表“用户”的“id”列的外键],subject_id[是表“id”列的外键”科目”]、年级、日期）

“用户”包括：（id、用户名、姓名、姓氏、密码、类型、状态、日期）

“主题”包括：（id、career_id、姓名、描述、小时数）

最后我想得到这样的东西：

我收到了这个错误：

这是我的代码：我的视图文件（“home”）：

    <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：/

【问题讨论】：

标签： php mysql codeigniter fetch

【解决方案1】：

我将您的查询更改为加入查询，只需将您的代码更改为以下

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

【讨论】：

不工作的朋友，看看：i.gyazo.com/8d302565d423beb88889571332c38edf.png i.gyazo.com/4304d4b9a42049ef0cd7c84195ab9575.png i.gyazo.com/e1536527e7e5268e0a252aa7ff5b77e4.png等等：/
不工作：S，看看队友：i.gyazo.com/e72a33aeca6237c5e8cc650110edeef5.png i.gyazo.com/8b3399abcd73a3466579aef9a83b5336.png i.gyazo.com/59f088209f05fdceb7303f655eddef11.png i.gyazo.com/97d6ef1ef32956f095a33643e021b4f2.png
它不能正常工作，我得到了这个图表：i.gyazo.com/2f71375bf5add0e5ca69e7d5e6c2df9f.png这是我的数据库（用户）i.gyazo.com/2178fc6d2c3d382a80b435d589a1a1b9.png
还有我的主题数据库：i.gyazo.com/5d08fa4ce2dd036872cc937fa906cd99.png
你在吗？

【解决方案2】：

未定义的索引和尝试获取属性非对象或多或少意味着相同的事情，即您没有获取正确的数据，或者您尝试获取的变量或索引未初始化或未定义，其原因可能是错误在查询或您正在运行的查询返回的空白数据中。

我想请求您像这样提取您的查询数据

$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，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，但我有时也会反驳双引号的问题，是的，我知道.. 双引号内的变量有效，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。尝试像这样调试你的查询，目前你有

"SELECT * FROM TABLE WHERE THIS = $THAT"

把这个改成

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

希望对你有用！

已编辑： （抱歉，我未能展示您自己代码中的示例）你的模型文件

  <?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);

}

【讨论】：

老兄，你能帮我处理一下我的代码吗？我对这一切有点头晕：S
很抱歉，如果我的回答使情况恶化，请问有什么可以帮忙的，兄弟你试过我的解决方案了吗？只需尝试在空白或错误查询上添加处理程序，以使您的索引不为空。它将解决您的问题，例如您正在尝试初始化$var['index'] = '' 和$var['index'] = $something 假设$something 是当您的代码在使用num_rows() 和null 检查查询响应后具有值时您的查询不起作用并在检查num_rows()==0 后返回空白值，它将修复。
我的意思是，我不明白你的回答：S。如果你可以加入我的代码，你会帮助我很多伙伴:)
大佬，说有错误，看一下：i.gyazo.com/cd71f5f651f842a98270e753bd8008fb.png i.gyazo.com/18a2eba4c428d3056f2fd0a67f003bf1.png
if(!empty($user[0]['username']){ 我错过了“)”关闭小括号，请把它放在上面，它会像这样if(!empty($user[0]['username'])){ - 更新答案并在那里添加小括号。