Laravel：完整性约束违规：1452 无法添加或更新子行：外键约束失败

Question

我的 Laravel 应用程序出现此错误：

无法添加或更新子行：外键约束失败

这是我的 2 张桌子

用户

Schema::create('users', function(Blueprint $table)
    {
        $table->increments('id');
        $table->string('username');
        $table->string('password');
        $table->string('firstname');
        $table->string('lastname');
        $table->string('middlename');
        $table->string('address');
        $table->string('birthday');
        $table->string('contact');
        $table->string('email');
        $table->enum('isAdmin', array(0,1))->default(0);
        $table->enum('isTeacher', array(0,1))->default(0);
        $table->timestamps();

    });

出席率

Schema::create('attendance', function(Blueprint $table)
        {
        $table->increments('id');
        $table->string('status');
        $table->string('comment');
        $table->integer('student_id')->unsigned();
        $table->foreign('student_id')->references('id')->on('users');
        $table->string('student_firstname');
        $table->string('student_lastname');
        $table->integer('teacher_id')->unsigned();
        $table->foreign('teacher_id')->references('id')->on('users');
        $table->string('teacher_firstname');
        $table->string('teacher_lastname');
        $table->timestamps();

这是我的模型

用户

class User extends Eloquent implements UserInterface, RemindableInterface {

use UserTrait, RemindableTrait;

/**
 * The database table used by the model.
 *
 * @var string
 */
protected $table = 'users';

/**
 * The attributes excluded from the model's JSON form.
 *
 * @var array
 */
protected $hidden = array('password', 'remember_token');


public function attendance()
{

        return $this->belongsTo('Attendance');


}

出席率

class Attendance extends Eloquent
{






    public function users()
    {

        return $this->hasMany('User');

    }


}

**最后这是我的控制器**

    public function postCreateAttendance()
{
    $validate = Validator::make(Input::all(), array(
        'status' => 'required'
    ));


    if ($validate->fails())
    {
        return Redirect::route('viewStudent')->withErrors($validate)->withInput();
    }
    else
    {

        //$student  = User::whereRaw('isTeacher = "0" and isAdmin = "0"')->get();

        //$teacher  = User::whereRaw('isTeacher = "1" and isAdmin = "0"')->get();

        $student = new User();
        $teacher = new User();
        $attendance = new Attendance();
        $student->save();
       $teacher->save();
       $attendance->save();



        $student->student_id = Input::get('3');
        $attendance->status = Input::get('status');
        $attendance->comment = Input::get('comment');
        $attendance->student_firstname = Input::get('student_first');
        $attendance->student_lastname = Input::get('student_last');
        $attendance->teacher_firstname = Input::get('teacher_first');
        $attendance->teacher_lastname = Input::get('teacher_last');

我也试过这个，但它给了我同样的错误。

public function sampleAttendance()

{

    User::find(1)->attendance()->insert(array(
        'status' => 'present',
        'comment' => 'none',
        'student_id' => '1',
        'student_firstname' => 'student_first',
        'student_lastname' => 'student_last',
        'teacher_firstname' => 'teacher_first',
        'teacher_lastname' => 'teacher_last'


        ));

请帮忙？ :(

Answer 1

在您的架构中，您已在 attendance 表中放置了完整性约束，也就是外键。

因此，您无法在不先添加student_id 和teacher_id 的情况下保存考勤记录。

这不起作用：

   $student = new User();
   $teacher = new User();
   $attendance = new Attendance();
   $student->save();
   $teacher->save();
   $attendance->save();

这将起作用：

   $student = new User();
   $teacher = new User();
   //Saves student model
   $student->save();
   $teacher->save();
   //Saves Attendance model in relationship with student and teacher model
   $attendance = new Attendance([
      'student_id' => $student->id,
      'teacher_id' => $teacher->id
   ]);
   $attendance->save();

为什么我不能将出勤模型与学生和教师模型相关联，然后将它们保存到数据库中？

查看 Laravel 框架问题：https://github.com/laravel/framework/issues/6437

已提出但尚未实施。