Cannot add foreign key constraint in laravel error

Question

I have a migration for my tags table like the below:

Schema::create('tags', function (Blueprint $table) {
            $table->increments('id');
            $table->char('tag' , 15);
});

Now, I have the following migration for my admin table in which i have a foreign key associated with my tags table , the migration is the following:

Schema::create('admin', function (Blueprint $table) {
    $table->char('tag' , 15);
    $table->foreign('tag')->references('tag')->on('tags');
});

Now when i run this migration i get the following error:

Both the tables are innodb i have changed this in the settings in laravel. But i still get a cannot add a foreign key constraint error. Why ??

[This SO answer](https://stackoverflow.com/questions/22615926/migration-cannot-add-foreign-key-constraint-in-laravel) addresses your concern. — theterminalguy, Feb 12 '17 at 17:09
Why aren't you referencing the id column instead of the tag column itself? Anyway, is the database clean? Because that error will happen if by creating the foreign key, the database loses it's integrity, so the fk cannot be created. — Marco Aurélio Deleu, Feb 12 '17 at 17:09
@DamianSimonPeter tried that appraoch .. does't work , had seen that thread ! — Alexander Solonik, Feb 12 '17 at 17:10
@DamianSimonPeter i don't understand what you mean by , is your database clean ? can you emphasis ? — Alexander Solonik, Feb 12 '17 at 17:11
@AlexanderSolonik are your tables empty or not? Why do you use `char` instead of `integer` for tag? Isn't it just an id of a tag? — shukshin.ivan, Feb 12 '17 at 18:27
@Paras No its not a duplicate .. because i cleared all my migrations and now i am running this migration on a new install . This is a genuinly different problem , please remove the duplicate :) — Alexander Solonik, Feb 12 '17 at 20:20
Try to run `composer dump-autoload` in command line and then migrate.. — lewis4u, Feb 12 '17 at 21:00

score 0 · Answer 1 · answered Feb 13 '17 at 06:26

0

Try

$table->foreign('tag')->references('id')->on('tags');

Because in tags table, the primary key is id.

answered Feb 13 '17 at 06:26

EddyTheDove

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Cannot add foreign key constraint in laravel error

1 Answers1