Laravel 迁移：无法添加外键约束

我正在尝试在Laravel中创建外键，但是当我使用

artisan

迁移表时，出现以下错误：

[Illuminate\Database\QueryException]
SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL
: alter table `priorities` add constraint priorities_user_id_foreign foreign 
key (`user_id`) references `users` (`id`))     

我的迁移代码如下：

优先级迁移文件

public function up()
{
    //
    Schema::create('priorities', function($table) {
        $table->increments('id', true);
        $table->integer('user_id');
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('priority_name');
        $table->smallInteger('rank');
        $table->text('class');
        $table->timestamps('timecreated');
    });
}

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

用户迁移文件

public function up()
{
    //
    Schema::table('users', function($table)
    {
    $table->create();
    $table->increments('id');
    $table->string('email');
    $table->string('first_name');
    $table->string('password');
    $table->string('email_code');
    $table->string('time_created');
    $table->string('ip');
    $table->string('confirmed');
    $table->string('user_role');
    $table->string('salt');
    $table->string('last_login');

    $table->timestamps();
    });
}

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

任何关于我做错了什么的想法，我现在就想知道，因为我有很多表需要创建，例如用户、客户、项目、任务、状态、优先级、类型、团队。理想情况下，我希望创建使用外键保存此数据的表，即

客户机\项目

和

项目\任务

等

---

希望有人能帮助我开始

分两步添加，最好也取消签名：

public function up()
{
    Schema::create('priorities', function($table) {
        $table->increments('id', true);
        $table->integer('user_id')->unsigned();
        $table->string('priority_name');
        $table->smallInteger('rank');
        $table->text('class');
        $table->timestamps('timecreated');
    });

   Schema::table('priorities', function($table) {
       $table->foreign('user_id')->references('id')->on('users');
   });

}

---

问题已经回答了，但希望这能帮助其他人

---

发生此错误是因为我在迁移表的原始表中以主键形式存在外键之前，首先创建了包含外键的迁移表。迁移按照运行

migrate:make

后生成的文件名指示的顺序执行。例如

2014\u 05\u 10\u 165709\u create\u student\u table.php

解决方案是按照此处的建议，将具有外键的文件重命名为比具有主键的文件更早的时间：

---

我想我还必须添加

$table->engine='InnoDB'
我发生此错误是因为-当我尝试创建的表是InnoDB时-我尝试将其关联到的外部表是MyISAM表
 在我的例子中，问题是主表中已经有记录，我强制新列不为NULL。因此，将->nullable（）添加到新列就成功了。在问题的例子中是这样的：

public function up()
{
    Schema::create('priorities', function($table) {
        $table->increments('id', true);
        $table->integer('user_id')->unsigned();
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('priority_name');
        $table->smallInteger('rank');
        $table->text('class');
        $table->timestamps('timecreated');
    });
}

$table->integer（'user_id'）->unsigned（）->nullable（）

或：

$table->unsignedInteger（'user_id'）->nullable（）

希望这对别人有帮助
 在我的例子中，我引用了字符串
用户id
列上的整数
id
列。我改变了：

$table->string（'user\u id'）

致：

$table->integer（'user_id'）->unsigned（）

希望它能帮助别人
 为了在laravel中添加外键约束，我做了以下工作：

按如下方式创建要作为外键的列：

$table->integer('column_name')->unsigned();
$table->integer（'column_name'）->unsigned（）
在（1）之后立即添加约束线，即

$table->integer（'column_name'）->unsigned（）；
$table->foreign（'column_name'）->references（'pk_of_other_table'）->on（'other_table'）
在我的例子中，问题在于迁移时间，创建迁移时要小心，首先创建子迁移，而不是基本迁移。因为若首先创建具有外键的基本迁移，将查找子表，而不会有表抛出异常

更多信息：

创建迁移时，它的开头有一个时间戳。假设您已经创建了一个迁移cat，因此它看起来像
2015\u 08\u 19\u 075954\u the\u cats\u time.php
，它有以下代码

<?php

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

class TheCatsTime extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('cat', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');  
            $table->date('date_of_birth');
            $table->integer('breed_id')->unsigned()->nullable(); 
        });

        Schema::table('cat', function($table) {
        $table->foreign('breed_id')->references('id')->on('breed');
      });
    }

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

除非创建相关表，否则无法添加关系。Laravel按迁移文件的日期运行迁移顺序。所以，如果您想创建一个与第二个迁移文件中存在的表的关系，它将失败

我也面临同样的问题，所以我最后又创建了一个迁移文件来指定所有关系

Schema::table('properties', function(Blueprint $table) {
        $table->foreign('user')->references('id')->on('users')->onDelete('cascade');
        $table->foreign('area')->references('id')->on('areas')->onDelete('cascade');
        $table->foreign('city')->references('id')->on('cities')->onDelete('cascade');
        $table->foreign('type')->references('id')->on('property_types')->onDelete('cascade');
    });

    Schema::table('areas', function(Blueprint $table) {
        $table->foreign('city_id')->references('id')->on('cities')->onDelete('cascade');
    });

在最初的问题提出几年后，使用Laravel5.1，我在这里遇到了同样的错误，因为我的迁移是用相同的日期代码由计算机生成的。我检查了所有建议的解决方案，然后进行重构以找到错误源

在下面的Laracast中，以及在阅读这些帖子时，我相信正确的答案与Vickies的答案类似，只是不需要添加单独的模式调用。您不需要将表设置为Innodb，我假设laravel正在这样做

迁移只需要正确计时，这意味着您将在需要外键的表的文件名中修改日期代码up（稍后）。或者，降低不需要外键的表的日期代码

修改日期代码的优点是迁移代码更易于阅读和维护

到目前为止，我的代码通过向上调整时间代码来推动需要外键的迁移

然而，我有数百个表，所以在最后我有最后一个表，只用于外键。只是为了让事情顺利进行。我假设我会将它们拉入正确的文件，并在测试它们时修改日期代码

例如：文件2016\u 01\u 18\u9999\u创建\u产品\u选项\u表格。这一个需要创建products表。看看文件名

 public function up()
{
    Schema::create('product_options', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('product_attribute_id')->unsigned()->index();
        $table->integer('product_id')->unsigned()->index();
        $table->string('value', 40)->default('');
        $table->timestamps();
        //$table->foreign('product_id')->references('id')->on('products');
        $table->foreign('product_attribute_id')->references('id')->on('product_attributes');
        $table->foreign('product_id')->references('id')->on('products');


    });
}

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

products表：这需要首先迁移。2015年1月18日000000日创建产品表

public function up()
{
    Schema::create('products', function (Blueprint $table) {
        $table->increments('id');

        $table->string('style_number', 64)->default('');
        $table->string('title')->default('');
        $table->text('overview')->nullable();
        $table->text('description')->nullable();


        $table->timestamps();
    });
}

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

最后是我临时用来解决问题的文件，我将在为我命名为9999_99_99_9999; u create_foreign_keys.php的模型编写测试时对其进行重构。这些钥匙在我取出时会被注释，但你明白了

    public function up()
    {
//        Schema::table('product_skus', function ($table) {
//            $table->foreign('product_id')->references('id')->on('products')->onDelete('cascade');
//    });

    }

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

我知道这是一个老问题，但请确保如果您使用的是参考文献，则定义了正确的支持引擎。为两个表设置innodb引擎，并为引用列设置相同的数据类型

$table->engine = 'InnoDB';

这么简单

如果您第一次创建了
'priorities'
迁移文件，则Laravel首先运行
'priorities'
，而
'users'
表不存在

如何向不存在的表添加关系

解决方案：从
“优先级”
表中拉出外键代码。您的迁移文件应如下所示：

public function up()
{
    Schema::create('priorities', function($table) {
        $table->increments('id', true);
        $table->integer('user_id')->unsigned();
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('priority_name');
        $table->smallInteger('rank');
        $table->text('class');
        $table->timestamps('timecreated');
    });
}


并添加到一个新的迁移文件中，这里是它的名称
public function up()
{        
    Schema::table('priorities', function (Blueprint $table) {          
        $table->foreign('user_id')
              ->references('id')
              ->on('users');                        
    });
}

$table->unsignedInt('column_name');
$table->foreign('column_name')->references('id')->on('table_name');

public function up()
{
    Schema::create('priorities', function($table) {
        $table->increments('id', true);
        $table->integer('user_id')->unsigned();
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('priority_name');
        $table->smallInteger('rank');
        $table->text('class');
        $table->timestamps('timecreated');
    });
}

$table->increments('column_name'); //is INTEGER and UNSIGNED

$table->integer('column_forein_name')->unsigned(); //this must be INTEGER and UNSIGNED
$table->foreign('column_forein_name')->references('column_name')->on('first_table_name');

$table->mediumIncrements('column_name'); //is MEDIUM-INTEGER and UNSIGNED

$table->mediumInteger('column_forein_name')->unsigned(); //this must be MEDIUM-INTEGER and UNSIGNED
$table->foreign('column_forein_name')->references('column_name')->on('first_table_name');

        $table->integer('user_id', false, true);

$table->bigIncrements('id');

$table->unsignedInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

$table->unsignedBigInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

composer dump-autoload

public function up()
{
    //
     Schema::create('priorities', function($table) {
        $table->increments('id', true);
        $table->integer('user_id');
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('priority_name');
        $table->smallInteger('rank');
        $table->text('class');
        $table->timestamps('timecreated');
    });
 }

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

app/database/migrations

$table->increments('id');

Schema::create('users', function (Blueprint $table){
    $table->increments('id');
    $table->string('name');
    $table->timestamps();

Schema::create('permissions', function (Blueprint $table){
    $table->increments('id');
    $table->UnsignedInteger('user_id'); // UnsignedInteger = "increments" in users table
    $table->boolean('admin');
    $table->boolean('enabled');
    $table->timestamps();

    // set up relationship
    $table->foreign('user_id')->reference('id')->on('users')->onDelete('cascade');
}

Schema::create('schools', function (Blueprint $table) {
    $table->integer('dcid')->index()->unque();
    $table->integer('school_number')->index(); // The important thing is that this is indexed
    $table->string('name');
    $table->string('abbreviation');
    $table->integer('high_grade');
    $table->integer('low_grade');
    $table->timestamps();
    $table->primary('dcid');
});

Schema::create('students', function (Blueprint $table) {
      $table->increments('id');
      $table->integer('dcid')->index()->unique()->nullable();
      $table->unsignedInteger('student_number')->nullable();
      $table->integer('schoolid')->nullable();
      $table->foreign('schoolid')->references('school_number')->on('schools')->onDelete('set null');
      // ...
});

1. Users table

    Schema::create('users', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->string('email')->unique();
            $table->timestamp('email_verified_at')->nullable();
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });

2. Roles Table
    Schema::create('roles', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->string('name')->unique();
        $table->string('display_name')->nullable();
        $table->string('description')->nullable();
        $table->timestamps();
    });

3. Table role_user
Schema::create('role_user', function (Blueprint $table) {
            $table->unsignedBigInteger('user_id');
            $table->unsignedBigInteger('role_id');
            $table->foreign('user_id')->references('id')->on('users')
                ->onUpdate('cascade')->onDelete('cascade');
            $table->foreign('role_id')->references('id')->on('roles')
                ->onUpdate('cascade')->onDelete('cascade');
            $table->primary(['user_id', 'role_id']);
        });

// ...

public function up()
{
    Schema::create('users', function (Blueprint $table) {

        $table->bigIncrements('id');

        $table->string('full_name');
        $table->string('email');
        $table->timestamps();
    });
}

// ...

public function up()
{
    Schema::create('role_user', function (Blueprint $table) {

        // this line throw QueryException "SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint..."
        // $table->integer('user_id')->unsigned()->index();

        $table->bigInteger('user_id')->unsigned()->index(); // this is working
        $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
    });
}

$table->engine = 'InnoDB';

$table->engine = 'MyISAM';

SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint

public function up()
{
    Schema::create('users', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->unsignedInteger('business_unit_id')->nullable();

        $table->string('name', 100);

        $table->foreign('business_unit_id')
                ->references('id')
                ->on('business_units')
                ->onDelete('cascade');

        $table->timestamps();
        $table->softDeletes();
        $table->engine = 'InnoDB'; # <=== see this line
    });
}

public function up()
{
    Schema::create('transactions', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->float('amount', 11, 2);
        $table->enum('transaction type', ['debit', 'credit']);
        $table->bigInteger('customer_id')->unsigned();      
        $table->timestamps();                 
    });

    Schema::table('transactions', function($table) {
        $table->foreign('customer_id')
              ->references('id')->on('customers')
              ->onDelete('cascade');
    });     
}

$table->unsignedBigInteger('user_id');
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');

Schema::table('posts', function (Blueprint $table) {
    $table->foreignId('user_id')->constrained()->onDelete('cascade');
});

public function up()
{
    Schema::create('doc_education', function (Blueprint $table) {
        $table->increments('id');
        $table->integer('uni_id')->unsigned()->nullable();
        $table->timestamps();
    });
}

    Schema::create('doc_universties', function (Blueprint $table) {
        $table->increments('id');
        $table->string('uni_name');
        $table->string('location')->nullable();
        $table->timestamps();

        //
    });



Schema::table('doc_education', function(Blueprint $table) {
        $table->foreign('uni_id')->references('id')
        ->on('doc_universties')->onDelete('cascade');
    });

    $tables = [
        'table_1',
        'table_2'
    ];

    foreach ($tables as $table) {
        \DB::statement('ALTER TABLE ' . $table . ' ENGINE = InnoDB');
    }