SQLSTATE[HY000]：一般错误：1364 字段“parent_id”没有默认值

Question

I'm building my own forum as practice, I set up Topic and Comment models with polymorphic relationship, a comment can belong to a topic or another comment , this is because I want to have nested comments. Another issue is when I reply to the topic I get the following error:

SQLSTATE[HY000]: General error: 1364 Field 'parent_id' doesn't have a default value (SQL: insert into comments ( user_id , body , commentable_id , commentable_type , updated_at , created_at ) values (1 <\p>ljlnlnlnlnlnllnlnlnlnlnln</p>, 1, App\Models\Topic, 2019-11-08 20:41:43, 2019-11-08 20:41:43))

My models and Migrations.

Topic model:

class Topic extends Model
{
    protected $table = 'topics';

    public function author()
    {
        return $this->belongsTo('App\Models\User', 'user_id');
    }

    public function comments()
    {
        return $this->morphMany('App\Models\Comment', 'commentable')->whereNull('parent_id');
    }
}

public function up()
{
    Schema::create('topics', function (Blueprint $table) {
        $table->increments('id');
        $table->unsignedInteger('user_id')->index();
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('title');
        $table->text('body');
        $table->string('url')->unique();
        $table->string('slug')->unique();
        $table->boolean('isVisible')->default(false);
        $table->timestamps();
    });
}

Comment model:

class Comment extends Model
{
    protected $table = 'comments';

    public function author()
    {
        return $this->belongsTo('App\Models\User', 'user_id');
    }

    public function replies()
    {
        return $this->hasMany('App\Models\Comment', 'parent_id');
    }
}

public function up()
{
    Schema::create('comments', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->integer('user_id')->unsigned();
        $table->integer('parent_id')->unsigned();
        $table->integer('commentable_id')->unsigned();
        $table->string('commentable_type');
        $table->text('body');
        $table->timestamps();
    });
}

Answer 1

The error is pretty obvious; the column parent_id doesn't have a value (you're not setting one, and there is no default). Either set the column as nullable , or pass a parent_id

In migration :

$table->integer('parent_id')->unsigned()->nullable();

Answer 2

Since a comment on a topic has no parent comment (not a reply) then the parent_id would be null, however your database schema doesn't allow it, make the column nullable

$table->integer('parent_id')->unsigned()->nullable();

or give it null as the default value

$table->unsignedInteger('parent_id')->default(null);

Hope this helps

Answer 3

i had this problem and solved by adding my column into fillable property

Add parent_id to the fillable array in your model Comment , to allow saving through create and massive methods

protected $fillable = ['parent_id'];

Answer 4

i am trying to insert data into database using laravel which gives me this error Illuminate \ Database \ QueryException (HY000) SQLSTATE[HY000]: General error: 1364 Field 'body' doesn't have a default value (SQL: insert into categories ( id , title , updated_at , created_at ) values (1, khan, 2019-11-09 13:14:21, 2019-11-09 13:14:21)). plz instruct me what to do