SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails - mysql

Question

i have reply_qs table and postqs table.Postqs_id is foreign key in reply_qs table.when i tried to save the reply_qs form data in database,its showed this error.
ERROR:
SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or
update a
child row: a foreign key constraint fails (fyp2.reply_qs, CONSTRAINT
reply_qs_postqs_id_foreign FOREIGN KEY (postqs_id) REFERENCES postqs
(id) ON DELETE CASCADE ON UPDATE CASCADE) (SQL: insert into reply_qs
(reply, updated_at, created_at) values (saann, 2017-09-22 15:35:03,
2017-09-22 15:35:03))
how i can solve it? and please explain why im getting this error.
reply_qs model :
protected $table = 'reply_qs';
protected $fillable = ['reply'];
public function postqs(){
return $this->hasMany('App\Postqs');
}
postqs model :
public function reply_qs(){
return $this->hasMany('App\Reply_qs');
}
store function:
public function store(Request $request){
$data = $request->all();
$postqs=($request->id);
$reply=Reply_qs::create($data);
$reply->postqs($id);
}
migration:
Schema::create('reply_qs', function (Blueprint $table) {
$table->increments('id')->unique();
$table->text('reply');
$table->timestamps('date');
});
DB::statement('SET FOREIGN_KEY_CHECKS=0;');
Schema::table('reply_qs',function(Blueprint $table)
{
$table->integer('postqs_id')->unsigned();
$table->foreign('postqs_id')->references('id')->on('postqs') -
>onDelete('cascade')->onUpdate('cascade');
});
DB::statement('SET FOREIGN_KEY_CHECKS=1;');

Answer 1

Your relationships are not correct.
Your Reply_qs model should have this relationship with Postqs
public function postqs()
{
return $this->belongsTo(Postqs::class);
}
Your store function does not look correct and should look something like this
public function store( Request $request )
{
$reply = new Reply_qs();
$reply->text = $request->get('text');
$reply->postqs_id = $request->get('postqs_id');
$reply->save();
}
In your store method, it looks like you are trying to associate the parent Postqs object with the Reply_qs.
You would do this like so
$reply->associate($post);
You need to pass the object and not the id
If you are still struggling with this double check your foreign keys are matching correctly, you may need to implement the association like so
public function postqs()
{
return $this->belongsTo(Postqs::class, 'postqs_id', 'id);
}