向迁移添加外键(Laravel)

// 创建 users 表
Schema::create('users', function (Blueprint $table) {
    $table->id();
    $table->string('name');
    $table->timestamps();
});

// 创建 posts 表
Schema::create('posts', function (Blueprint $table) {
    $table->id();
    $table->string('title');
    $table->text('content');
    $table->unsignedBigInteger('user_id'); // 外键
    $table->timestamps();

    // 添加外键约束
    $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
});

// User 模型
class User extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

// Post 模型
class Post extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

// 示例：插入数据时确保 user_id 存在
$user = User::find(1); // 确保 user_id 存在
$post = new Post([
    'title' => 'Example Post',
    'content' => 'This is an example post.',
    'user_id' => $user->id,
]);
$post->save();

// 示例：添加索引
Schema::table('posts', function (Blueprint $table) {
    $table->index('user_id');
});