php - Laravel 5.1 外键迁移错误

Question

我在执行约束迁移时遇到了这个奇怪的错误当我执行此迁移时，我得到

 [Illuminate\Database\QueryException]
  SQLSTATE[HY000]: General error: 1005 Can't create table 'flowtime_dev.#sql-85bb_52' (errno: 121) (SQL: alter table `questions` add constraint questions_inventory_i
  d_foreign foreign key (`inventory_id`) references `inventories` (`id`) on delete cascade)



  [PDOException]
  SQLSTATE[HY000]: General error: 1005 Can't create table 'flowtime_dev.#sql-85bb_52' (errno: 121)

我读到过不同表中的数据类型应该匹配(比如 int(10) 到 int(10))，它们确实匹配，这也是我进行的最后一次迁移(所有表都存在并已创建之前的其他迁移)。

我真的不知道该怎么做了:(。有人可以帮忙吗？我看过类似的帖子，但到目前为止他们还没有为我解决问题。

迁移如下:

public function up()
    {
        Schema::table('questions', function ($table) {
            $table->integer('inventory_id')->unsigned()->change();
            $table->foreign('inventory_id')
                ->references('id')->on('inventories')
                ->onDelete('cascade');  
        });

        Schema::table('question_response', function ($table) {
            $table->integer('question_id')->unsigned()->change();
            $table->foreign('question_id')
                ->references('id')->on('questions')
                ->onDelete('cascade');
        });

        Schema::table('question_response', function ($table) {
            $table->integer('sample_result_set_id')->unsigned()->change();             
            $table->foreign('sample_result_set_id')
                ->references('id')->on('sample_response_set')
                ->onDelete('cascade');
        });

        Schema::table('inventory_response', function ($table) {
            $table->integer('inventory_id')->unsigned()->change();  
            $table->foreign('inventory_id')
                ->references('id')->on('inventories')
                ->onDelete('cascade');
        });

        Schema::table('inventory_response', function ($table) {
            $table->integer('sample_result_set_id')->unsigned()->change(); 
            $table->foreign('sample_result_set_id')
                ->references('id')->on('sample_response_set')
                ->onDelete('cascade');
        });

    }

Answer 1

在迁移开始时关闭外键约束。

SET FOREIGN_KEY_CHECKS=0;

然后，在迁移数据后，将它们重新打开。

SET FOREIGN_KEY_CHECKS=1;

如果这不起作用，请尝试添加以下行。

$table->engine = 'InnoDB'

Further, you can rename the constraint since the name may already be used...

$table->foreign('inventory_id', 'fk_questions_inventory_id')->...