@mrlanphear Hi， I got the same problem, how did you solve it? Also, ask @jeffreyway for help~~ Thanks in advance.

php artisan tinker
Psy Shell v0.10.9 (PHP 8.0.10 — cli) by Justin Hileman
>>> use App\Models\Post;
>>> Post::create([
... 'title'=> 'My Family Post',
... 'excerpt'=> 'Excerpt for my post',
... 'body'=>'Lorem ipsum dolar sit amet.',
... 'slug'=>'my-family-post',
... 'category_id'=> 1,
... ]);
Illuminate\Database\QueryException with message 'SQLSTATE[HY000]: General error: 1364 Field 'category_id' doesn't have a default value (SQL: insert into `posts` (`title`, `excerpt`, `body`, `updated_at`, `created_at`) values (My Family Post, Excerpt for my post, Lorem ipsum dolar sit amet., 2021-10-29 03:26:17, 2021-10-29 03:26:17))'

In /database/migrations/..._create_posts_table.php

    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->foreignid('category_id');
            $table->string('slug')->unique();
            $table->string('title');
            $table->text('excerpt');
            $table->text('body');

            $table->timestamps();
            $table->timestamp('published_at')->nullable();
        });
    }

and in /Models/post.php

class Post extends Model
{
    use HasFactory;

//    protected $fillable= ['title', 'excerpt', 'body','slug','category_id'];

    protected $guarded= [];
    public function getRouteKeyName()
    {
        return 'slug';
    }

}

Your First Eloquent Relationship

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