关于mysql：Laravel 5.1迁移和种子无法截断外键约束中引用的表

Laravel 5.1 Migration and Seeding Cannot truncate a table referenced in a foreign key constraint

我正在尝试运行迁移(见下文)并为数据库播种，但是当我运行时

1	php artisan migrate --seed

我收到此错误：

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Migration table created successfully.
Migrated: 2015_06_17_100000_create_users_table
Migrated: 2015_06_17_200000_create_password_resets_table
Migrated: 2015_06_17_300000_create_vehicles_table

[Illuminate\Database\QueryException]
SQLSTATE[42000]: Syntax error or access violation: 1701 Cannot truncate a table
referenced in a foreign key constraint (`app`.`vehicles`, CONSTRAINT `vehic
les_user_id_foreign` FOREIGN KEY (`user_id`) REFERENCES `app`.`users` (`id`
)) (SQL: truncate `users`)

[PDOException]
SQLSTATE[42000]: Syntax error or access violation: 1701 Cannot truncate a table
referenced in a foreign key constraint (`app`.`vehicles`, CONSTRAINT `vehic
les_user_id_foreign` FOREIGN KEY (`user_id`) REFERENCES `app`.`users` (`id`
))

我查看了这个错误应该是什么意思，并且还找到了遇到同样问题的其他人的例子，甚至只是与使用MySQL及其解决方案有关，但是应用：

1 2	DB::statement('SET FOREIGN_KEY_CHECKS=0;'); and DB::statement('SET FOREIGN_KEY_CHECKS=1;');

在down()中似乎不起作用，当我在MySQL中运行describe时，表格看起来是正确的。

正确命名迁移以确保首先迁移users表，然后确定可以应用外键的车辆，并且正确设置的表表明迁移已运行，但随后发生错误。我删除并重新创建了数据库并再次尝试，结果相同。我也不明白为什么它试图截断数据库的第一个迁移和种子，我不会想到当你试图运行php artisan migrate：refresh --seed时会发生这种情况。

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// 2015_06_17_100000_create_users_table.php

class CreateUsersTable extends Migration
{
public function up()
{
Schema::create('users', function (Blueprint $table) {
$table->increments('id');
$table->string('username', 60)->unique();
$table->string('email', 200)->unique();
$table->string('password', 255);
$table->string('role')->default('user');
$table->rememberToken();
$table->timestamps();
});
}
}

public function down()
{
Schema::drop('users');
}

// 2015_06_17_300000_create_vehicles_table.php

class CreateVehiclesTable extends Migration
{
public function up()
{
Schema::create('vehicles', function (Blueprint $table) {
$table->increments('id');
$table->integer('user_id')->unsigned();
$table->string('make');
$table->string('model');
$table->string('year');
$table->string('color');
$table->string('plate');
$table->timestamps();

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

public function down()
{
Schema::drop('vehicles');
}