对Laravel模型关系插入应用一些约束

// 在 posts 表中定义 user_id 字段为外键，引用 users 表的 id 字段
Schema::create('posts', function (Blueprint $table) {
    $table->id();
    $table->unsignedBigInteger('user_id');
    $table->string('title');
    $table->text('content');
    $table->timestamps();

    $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
});

Schema::create('users', function (Blueprint $table) {
    $table->id();
    $table->string('email')->unique();
    $table->string('password');
    $table->timestamps();
});

Schema::create('users', function (Blueprint $table) {
    $table->id();
    $table->string('name');
    $table->integer('age')->check('age >= 0 AND age <= 150');
    $table->timestamps();
});

Schema::create('users', function (Blueprint $table) {
    $table->id();
    $table->string('name');
    $table->boolean('is_active')->default(true);
    $table->timestamps();
});

Schema::create('users', function (Blueprint $table) {
    $table->id();
    $table->string('name')->nullable(false);
    $table->string('password')->nullable(false);
    $table->timestamps();
});

DB::transaction(function () {
    $user = User::create(['name' => 'John Doe']);
    Post::create(['title' => 'My First Post', 'content' => '...', 'user_id' => $user->id]);
});

$user = User::firstOrCreate(['email' => 'john@example.com'], ['name' => 'John Doe']);