违反Laravel - Integrity约束: 1452

Question

这是我的迁移：

public function up()
    {
      Schema::table('payments', function($table)
      {
        $table->dropColumn('invoice_id');
      });
    }

     public function down()
    {
      Schema::table('payments',function (Blueprint $table){
        $table->unsignedInteger('invoice_id')->index();
        $table->foreign('invoice_id')->references('id')->on('invoices')->onDelete('cascade');
      });
    }

当我运行php artisan migrate:rollback时，它给出了这个异常：

[Illuminate\Database\QueryException]                                                                                                         
  SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`invoiceninja`.`#sq  
  l-418_46`, CONSTRAINT `payments_invoice_id_foreign` FOREIGN KEY (`invoice_id`) REFERENCES `invoices` (`id`) ON DELETE CASCADE) (SQL: alter   
  table `payments` add constraint `payments_invoice_id_foreign` foreign key (`invoice_id`) references `invoices` (`id`) on delete cascade)     



  [PDOException]                                                                                                                               
  SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`invoiceninja`.`#sq  
  l-418_46`, CONSTRAINT `payments_invoice_id_foreign` FOREIGN KEY (`invoice_id`) REFERENCES `invoices` (`id`) ON DELETE CASCADE)       

有人能帮我吗？

Answer 1

我假设您正在运行down方法。第一行：

$table->unsignedInteger('invoice_id')->index();

添加回列，我不知道Laravel，但我猜这会为该列分配一个默认值0。

$table->foreign('invoice_id')->references('id')->on('invoices')->onDelete('cascade');

如果引用的id列中没有0值，则会失败。

您可能可以通过允许invoice_id列为NULL并将其用作默认值来实现这一点。

我的第一步是检查新添加的列invoice_id中的值。

Answer 2

我不确定为什么在down()方法中有这个逻辑，因为它通常是在up()中，但请尝试这样做：

public function down()
{
    Schema::table('payments', function (Blueprint $table){
        $table->unsignedInteger('invoice_id')->index();
    });

    Schema::table('payments', function (Blueprint $table){
        $table->foreign('invoice_id')->references('id')->on('invoices')->onDelete('cascade');
    });
}