SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row in Laravel9

Question

I have an integrity constraint violation when I run the php artisan db:seed command in Laravel 9.

Error

PDOException::("SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (hunger-db.restaurants, CONSTRAINT restaurants_user_id_foreign FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE)")

setup_users_table

public function up()
{
    Schema::create('users', function (Blueprint $table) {
        $table->id();
        $table->string('name');
        $table->string('email')->unique();
        $table->timestamp('email_verified_at')->nullable();
        $table->string('password');
        $table->string('phone');
        $table->tinyInteger('role_as')->default('0');
        $table->tinyInteger('gender')->default('0');
        $table->string('date_of_birth')->default('1999/9/9');
        $table->rememberToken();

        $table->timestamps();
    });
}

setum_restaurants_table

public function up()
{
    Schema::create('restaurants', function (Blueprint $table) {
        $table->id();
        $table->string('name');
        $table->string('img_src');
        $table->string('description');
        $table->string('minimum_order_amount');
        $table->string('working_hours_open');
        $table->string('working_hours_close');
        $table->string('delivery_time');
        $table->string('delivery_fee');
        $table->boolean('status')->default('0');
        $table->unsignedBigInteger('user_id')->default('1');
        $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
        $table->timestamps();
    });
}

User Model

class User extends Authenticatable
{
    use HasApiTokens, HasFactory, Notifiable;

    protected $fillable = [
        'name',
        'email',
        'password',
        'phone',
    ];

    public function orders()
    {
        return $this->hasMany(Order::class);
    }

    public function restaurants()
    {
        return $this->belongsTo(Restaurant::class);
    }
}

Restaurant Model

class Restaurant extends Model
{
    use HasFactory;

    protected $fillable = [
        'name',
        'img_src',
        'description',
    ];
    public function users()
    {
        return $this->belongsTo(User::class);
    }
}

Answer 1

I see some things to change here

setup_restaurants_table

I don't see with good eyes user_id with default 1, maybe is better to define the value when restaurant is created or manually assign it to user 1.

Schema::create('restaurants', function (Blueprint $table) {
        $table->id();
        ...
        $table->foreignId('user_id')->constrained()->onDelete('CASCADE');
});

After DB changes run php artisan migrate:fresh

User.php

Should change relation to hasMany Restaurants

public function restaurants()
{
    return $this->hasMany(Restaurant::class);
}

Seeding

Also ensure your DB seeding is correct, I mean creating user first and then restaurant, set user_id with an existing value.

Maybe creating a restaurant like this:

$user = User::factory()
            ->hasRestaurants(3)
            ->create();

If any factory change run php artisan db:seed

Can also see Factory Retationship Docs

Answer 2

Check the user_id you have added to the restaurants table. Make sure it exists in the Users table. Maybe my english not enough to tell you, can check another answer for the problem.