"General error: 1005 Can't create table" Using Laravel Schema Build and Foreign Keys

I've been having the same problem. I just noticed the following note at the very bottom of the Laravel Schema docs:

Note: The field referenced in the foreign key is very likely an auto increment and therefore automatically an unsigned integer. Please make sure to create the foreign key field with unsigned() as both fields have to be the exact same type, the engine on both tables has to be set to InnoDB, and the referenced table must be created before the table with the foreign key.

For me, as soon as I set my foreign key fields as such:

$table->integer('author')->unsigned();

I had no problem.

EDIT: Also, make sure that the fields in the foreign table are already created, otherwise this may fail with the same error.

I'm not 100% sure if these are the reasons this is failing but a couple of pointers. If you're using an older version of mySQL as the database, the default table implementation is myISAM that does not support foreign key restraints. As your scripts are failing on the foreign key assignment, you are better off explicitly stating that you want INNODB as the engine using this syntax in Schema's create method.

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

    $table->increments('id');
    $table->string('title')->nullable();
    $table->string('summary')->nullable();
    $table->timestamps();
});

This should hopefully alleviate the problems you are having.

Also, whilst you can declare foreign keys as an afterthought, I create the foreign keys within the initial schema as I can do an easy check to make sure I've got the right DB engine set.

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

    $table->increments('id');
    $table->integer('author');
    $table->integer('lesson');
    $table->string('title')->nullable();
    $table->string('summary')->nullable();
    $table->string('tagline')->nullable();
    $table->text('content')->nullable();
    $table->text('attachments')->nullable();
    $table->timestamps();

    $table->foreign('author')->references('id')->on('users');
    $table->foreign('lesson')->references('id')->on('lessons');
});

Hope this helps / solves your problem.

A Summary of the answers already listed, plus mine:

1. Foreign Keys generally require InnoDb, so set your default engine, or explicitly specify

   $table->engine = 'InnoDB';
   

2. 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.

3. 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).

4. 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).