将外键添加到Laravel中的现有表时，外键约束失败

Question

我有一个表order_lines，该表的order_id属于订单。现在，我忘记了将外键添加到初始迁移中，现在网站已启动并正在运行，并且数据库中有生命数据。

我想添加的外键会在删除订单时删除订单行。

我创建了以下迁移add_order_lines_order_id_foreign_to_order_lines_table

class AddOrderLinesOrderIdForeignToOrderLinesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('order_lines', function (Blueprint $table) {
            $table->foreign('order_id', 'order_lines_order_id_foreign')->references('id')->on('orders')
                ->onDelete('cascade');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('order_lines', function (Blueprint $table) {
            $table->dropForeign('order_lines_order_id_foreign');
        });
    }
}

唯一要做的是（尝试）添加外键约束，以便将来的订单被删除时，order_lines也随之删除。

这是我尝试运行迁移时收到的错误

SQLSTATE [23000]：违反完整性约束：1452无法添加或更新子行：外键约束失败（bud001_miguel。＃sql-5e1_109923，CONSTRAINT order_lines_order_id_foreign外键（order_id）参考订单（id）删除级联）（ SQL：更改表order_lines添加约束order_lines_order_id_foreign外键（order_id）引用删除级联上的订单（id））

这是原始的orders表定义

class CreateOrdersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('orders', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->unsignedBigInteger('user_id')->nullable();
            $table->unsignedBigInteger('shipping_address_id')->nullable();
            $table->unsignedBigInteger('billing_address_id')->nullable();
            $table->text('shipping_address_data')->nullable();
            $table->text('billing_address_data')->nullable();
            $table->timestamps();
        });

        Schema::table('orders', function (Blueprint $table) {
            $table->foreign('user_id')->references('id')->on('users')->onDelete('set null');
            $table->foreign('shipping_address_id')->references('id')->on('addresses')->onDelete('set null');
            $table->foreign('billing_address_id')->references('id')->on('addresses')->onDelete('set null');
        });
    }

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

这是原始的order_lines表定义

class CreateOrderLinesTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('order_lines', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->unsignedBigInteger('order_id');
            $table->unsignedBigInteger('animal_id');
            $table->unsignedBigInteger('product_plan_id');
            $table->unsignedInteger('price');
            $table->unsignedInteger('daily_price');
            $table->text('animal_data')->nullable();
            $table->text('plan_data')->nullable();
            $table->timestamps();
        });
    }

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

我尝试过的

• 通过在迁移中添加以下语句来禁用外键检查DB::statement('SET FOREIGN_KEY_CHECKS=0;');

但是错误仍然存​​在。

Answer 1

您的问题是order_lines表中有一些带有order_id的记录，这些记录在orders表中不存在。

Answer 2

$table->index('order_id');

$table->foreign('order_id')->references('id')->on('orders')->onDelete('cascade');