Foreign keys in Laravel 4 migrations issue

问题

I've just created a new Laravel 4 project and am finding strange things happening with the foreign key aspect of the schema builder. If I use the ->foreign() method in any of my migrations I get thrown MySQL errors 150 and general error 1005. According to the documentation at laravel.com/docs the two scenario's at the bottom should work? Anyone know why they don't?

The following does work:

    Schema::create('areas', function($table)
    {
        $table->engine ='InnoDB';
        $table->increments('id');

        $table->integer('region_id')->references('id')->on('regions');

        $table->string('name', 160);
        $table->timestamps();
    });

But these two do not work:

    Schema::create('areas', function($table)
    {
        $table->engine ='InnoDB';
        $table->increments('id');

        $table->foreign('region_id')->references('id')->on('regions');

        $table->string('name', 160);
        $table->timestamps();
    });

    Schema::create('areas', function($table)
    {
        $table->engine ='InnoDB';
        $table->increments('id');

        $table->integer('region_id');
        $table->foreign('region_id')->references('id')->on('regions');

        $table->string('name', 160);
        $table->timestamps();
    });

回答1:

Check your id type. Laravel 4 creates an incremental id with a int(10) unsigned. If you create a basic integer and try to put a foreign key on it, it will fail.

As suggested in the documentation at this link, you should create the foreign id with $table->unsignedInteger(YOUR_ID_NAME); to make it work.

回答2:

Also some answers over at this question "General error: 1005 Can't create table" Using Laravel Schema Build and Foreign Keys

A Summary of the answers listed there, including mine:

Foreign Keys generally require InnoDb, so set your default engine, or explicitly specify $table->engine = 'InnoDB'; If your table is already created and has defaulted to MyISAM, you may need to alter it.
Foreign keys require the referenced table to exist. Make sure the referenced table is created in an earlier migration, prior to creating the key. Consider creating the keys in a separate migration to be sure.
Foreign Keys require the data type to be congruent. Check whether the referenced field is the same type, whether its signed or unsigned, whether it's length is the same (or less).
If you are switching between hand coding migrations, and using generators, make sure you check the id type you are using. Artisan uses increments() by default but Jeffrey Way appears to prefer integer('id', true).

回答3:

Had same problem day ago.

Root of problem is : column with foreign key must be same type as that key. And you have different types: INT/UNSIGNED INT

this makes id an UNSIGNED INT

$table->increments('id');

and this makes region_id an INT

$table->integer('region_id')->references('id')->on('regions');

To solve this, make region_id an UNSIGNED INT too

$table->integer('region_id')->unsigned()->references('id')->on('regions'); 
                              ^^^^^^^^^ note here

Documentation of Laravel has mention about this :

Note: When creating a foreign key that references an incrementing integer, remember to always make the foreign key column unsigned.

回答4:

It works, but sometimes you just have to be careful and try to understand what is happening behind the scene.

As I said in my comment. When you first ran the migration without creating the related column, Laravel migration services created your table and then, when you tried to migrate again it will always give you an error saying that the table already exists.

So you just have to drop table areas and run php artisan migrate again to fix it all.

EDIT:

I just created your migration (below) here and it worked.

As you can see I'm not using MySQL, so it must be a MySQL problem. Check MySQL foreign key documentation to see if your metadata fits in InnoDB requirements: http://dev.mysql.com/doc/refman/5.6/en/innodb-foreign-key-constraints.html.

<?php

use Illuminate\Database\Migrations\Migration;

class CreateAreasTable extends Migration {

    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('regions', function($table)
         {
             // $table->engine = 'InnoDB';
             $table->increments('id');
             $table->string('name', 160)->unique();
             $table->timestamps();
        });

        Schema::create('areas', function($table)
        {
            // $table->engine ='InnoDB';
            $table->increments('id');

            $table->integer('region_id');
            $table->foreign('region_id')->references('id')->on('regions');

            $table->string('name', 160);
            $table->timestamps();
        });     
    }

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

}

回答5:

antonio carlos is right, make sure that you created first the reference table of your foreign key.

try migrate first the tables without foreign keys , then make another migration assigning the foreign keys. on this state, laravel is sure that the reference key(s) are existing. and you dont have to drop tables during the artisan errors.

来源：https://stackoverflow.com/questions/16928740/foreign-keys-in-laravel-4-migrations-issue

标签

mysql

laravel

laravel-4