Laravel 的上下迁移方法是如何工作的？

How does Laravel's migration up and down method work?

提问by Deeven

In this code the table is created in the up method and deleted in the down() method. When I run the migration, the table is created but not deleted. In what way can I trigger the down method, so that I get a better understanding on how the two methods work?

在这段代码中，表是在 up 方法中创建的，并在 down() 方法中删除。当我运行迁移时，表被创建但没有被删除。我可以通过什么方式触发down方法，以便更好地了解这两种方法的工作原理？

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateFlightsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('flights', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('airline');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('flights');
    }
}

回答by mikemols

In your example:

在你的例子中：

php artisan migratewill run your up()method.

php artisan migrate将运行您的up()方法。

php artisan migrate:rollbackwill run your down()method.

php artisan migrate:rollback将运行您的down()方法。

Read up on the excellent docs: https://laravel.com/docs/5.7/migrations#migration-structure

阅读优秀的文档：https: //laravel.com/docs/5.7/migrations#migration-structure

回答by Felipe Perucci M. Do Amaral

Try:

尝试：

public function down()
{
    Schema::dropIfExists('flights');
}

回答by yosober

You sohuld add dropIfExistsinstead of drop

你应该添加dropIfExists而不是drop

and if you wanna just drop the specific migration file you should write your code in command like this:

如果您只想删除特定的迁移文件，您应该在命令中编写代码，如下所示：

php artisan migrate:rollback --path=\database\migrations\flights.php