Laravel：违反完整性约束：1452 无法添加或更新子行：外键约束失败

Laravel: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails

提问by Virgil Cruz

im having this error on my Laravel Application:

我的 Laravel 应用程序出现此错误：

Cannot add or update a child row: a foreign key constraint fails

无法添加或更新子行：外键约束失败

Here are my 2 tables

这是我的 2 张桌子

Users

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();

    });

Attendance

出勤率

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();

Here's my models

这是我的模型

User

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');


}

Attendance

出勤率

class Attendance extends Eloquent
{






    public function users()
    {

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

    }


}

**And finally here's my controller **

**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');

I tried this too as well and its giving me the same error.

我也试过这个，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'


        ));

Please help? :(

请帮忙？:(

回答by Mysteryos

In your schema, you have placed integrity constraints, aka foreign keys in your attendancetable.

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

Therefore you cannotsave an attendance record without adding its student_idand teacher_idfirst.

因此，您不能在不先添加student_id和的情况下保存考勤记录teacher_id。

This will not work:

这将不起作用：

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

This will work:

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();

Why can't i just associate the attendance model with the student and teacher models and then save them to the DB?

为什么我不能将考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？

See Laravel Framework Issue: https://github.com/laravel/framework/issues/6437

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

It's been proposed but not yet implemented.

已提出但尚未实施。