Laravel 5.1 Migration and Seeding Cannot truncate a table referenced in a foreign key constraint

Question

I\'m trying to run the migration (see below) and seed the database, but when I run

php artisan migrate --seed

I get this error:

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Answer 1

You could just drop it with.

$table->dropForeign('posts_user_id_foreign');

Answer 2

you can use

DB::table('your_table_name')->delete();

to empty a table, this won't delete the table structure. But the auto increment id will not start from initial number.

Answer 3

Here is what works for me every time. When you're adding the foreign key, make sure to add cascade. the syntax is like this

$table->foreign('column')->references('id')->on('table_name')->onDelete('cascade');

Make sure to replace id with whatever field is applicable for you.

Now before running the seeding add this instead of trucate

DB::statement('DELETE FROM table_name');

It will delete all the data. Hope this helps.

Answer 4

As the error says, you can not truncate tables referenced by foreign keys. Delete should work though...

DB::table('some_table')->delete();

Answer 5

DB::statement('SET FOREIGN_KEY_CHECKS=0;');
App\User::truncate();
DB::statement('SET FOREIGN_KEY_CHECKS=1;');

And it works！

Answer 6

I faced the same issue with my Role and Permission setup and this is what I did that worked as I wanted. Truncate() will reset the Increment column to 1 but throw a foreign key error while delete on the other hand works fine but doesn't reset the increment column, so I did the following in my Seeder's file (i.e RoleSeeder.php in my case)

1. [ delete() method ]

$roles = [];

... // Some foreach statement to prepare an array of data for DB insert()

// Delete and Reset Table
DB::table('roles')->delete();
DB::statement("ALTER TABLE `roles` AUTO_INCREMENT = 1");
// Insert into table
DB::table('roles')->insert($roles);

This will cascade all other child tables attached to the roles table. in my case users_roles table. This way I avoided disabling and enabling foreign key checks.

2. Something to put in mind / Second Approach [ truncate() method ]

if you don't have the intention of deleting all the data stored in the child's table (in my case users_roles table) ... You can go with truncate() and then in the DatabaseSeeders.php file you disable and enable foreign key check. As I tested this and the users_roles data was intact, the seed on affected roles table.

//RoleSeeders.php File

$roles = [];

... // Some foreach statement to prepare an array of data for DB insert()

// Truncate Table
DB::table('roles')->truncate();
// Insert into table
DB::table('roles')->insert($roles);

Then in the DatabaseSeeder.php file, you do;

public function run()
{
    DB::statement('SET FOREIGN_KEY_CHECKS=0;');

    $this->call([
        RoleSeeder::class,
    ]);

    DB::statement('SET FOREIGN_KEY_CHECKS=1;');
}

But I prefer the delete() method better, since I don't have to disable/enable the foreign key check