错误 1215；不断收到此外键错误

Question

我在 Whosebug 上看到了很多关于我的错误的问题，但出于某种原因，答案不适用于以下内容：

我有如下三个表格：

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

        $table->increments('id');
        $table->integer('activity_id')->unique();
        $table->string('title');
        $table->string('location');
        $table->string('price');
        $table->string('age_indication')->nullable();
        $table->longText('registration')->nullable();
        $table->longText('mandatory')->nullable();
        $table->longText('description')->nullable();
        $table->string('special_title')->nullable();
        $table->string('academy')->nullable();
        $table->timestamps();

        $table->integer('en_table')->nullable();
        $table->integer('de_table')->nullable();
    });
}

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

        $table->increments('id');
        $table->integer('activity_id')->unique();
        $table->string('title');
        $table->string('location');
        $table->string('age_indication')->nullable();
        $table->string('price');
        $table->longText('registration')->nullable();
        $table->longText('mandatory')->nullable();
        $table->longText('description')->nullable();
        $table->string('special_title')->nullable();
        $table->string('academy')->nullable();
        $table->timestamps();

        $table->integer('nl_table')->nullable();
        $table->integer('en_table')->nullable();
    });
}

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

        $table->increments('id');
        $table->integer('activity_id')->unique();
        $table->string('title');
        $table->string('location');
        $table->string('age_indication')->nullable();
        $table->string('price');
        $table->longText('registration')->nullable();
        $table->longText('mandatory')->nullable();
        $table->longText('description')->nullable();
        $table->string('special_title')->nullable();
        $table->string('academy')->nullable();
        $table->timestamps();

        $table->integer('nl_table')->nullable();
        $table->integer('de_table')->nullable();
    });
}

我尝试通过 increments('id') 而非 integer('activity_id) 来连接它们。下面是连接外键的迁移。

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

        $table->foreign('en_table')->references('activity_id')->on('activities_en');
        $table->foreign('de_table')->references('activity_id')->on('activities_de');
    });

    Schema::table('activities_de', function(Blueprint $table){

        $table->foreign('en_table')->references('activity_id')->on('activities_en');
        $table->foreign('nl_table')->references('activity_id')->on('activities_nl');
    });

    Schema::table('activities_en', function(Blueprint $table){

        $table->foreign('nl_table')->references('activity_id')->on('activities_nl');
        $table->foreign('de_table')->references('activity_id')->on('activities_de');
    });
}

出于某种原因，我一直收到外键约束。是因为 laravel 不喜欢我尝试引用不同的 ID 吗？如果是这样，是否有解决方法..

还是我忽略了一个拼写错误？

编辑：对于所有应该是外来的列，从 unsignedInteger 更改为仅整数。编辑：将 ->nullable() 添加到 activity_id 因此它与其他列完全相同

编辑：感谢@shadow，我发现 activity_id 上没有索引。我所要做的就是让它独一无二。

Answer 1

问题是 activity_id 被定义为整数，而保存外键的字段被定义为无符号整数。这是类型不匹配。所有字段都应定义为整数或无符号整数。

参见 mysql 关于 foreign keys 的文档：

Corresponding columns in the foreign key and the referenced key must have similar data types. The size and sign of integer types must be the same. The length of string types need not be the same. For nonbinary (character) string columns, the character set and collation must be the same.

此外，您需要在引用字段和被引用字段上创建索引，以便设置外键。 Mysql 仅在引用字段不存在时才创建索引：

MySQL requires indexes on foreign keys and referenced keys so that foreign key checks can be fast and not require a table scan. In the referencing table, there must be an index where the foreign key columns are listed as the first columns in the same order. Such an index is created on the referencing table automatically if it does not exist.

错误 1215；不断收到此外键错误

Error 1215; keep getting this foreign key error

php

mysql

laravel-5.2