将外键添加到表

Question

I want to add a foreign key to a table in my sql database in laravel. But after adding I get the following error:

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

The table where I am adding this key to is this:

public function up()
{
    Schema::create('userroles', function(Blueprint $table)
    {
        $table->increments('id');
        $table->string('user_id');
        $table->foreign('user_id')->references('user_id')->on('users');
        $table->string('role_id');
        $table->timestamps();

    });
}

And the table where I am referring to:

public function up()
{
    Schema::create('users', function(Blueprint $table)
    {
        $table->increments('id');
        $table->string('user_id');
        $table->string('name');
        $table->smallInteger('is_responder')->default(0);
        $table->string('email')->unique();
        $table->string('password', 60);
        $table->rememberToken();
        $table->timestamps();
    });
}

The name and the type are the same. What else could it be that I get the error?

Update The field "user_id" in the users table will be a GUID specifically created to each user. This is the field I would like to reference to within other tables. Is this possible? So do I need to make this field a PK then, as far as I understand?

Answer 1

You can create foreign key to id column of users table.

Instead of:

$table->string('user_id');
$table->foreign('user_id')->references('user_id')->on('users');

Use:

$table->integer('user_id')->unsigned();
$table->foreign('user_id')->references('id')->on('users');