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Truncate tables with foreign key constraints in a Laravel seed file.

For the scenario, imagine posts has a foreign key user_id referencing users.id

public function up()
{
	Schema::create('posts', function(Blueprint $table) {
		$table->increments('id');
		$table->string('title');
		$table->text('body');
		$table->integer('user_id')->unsigned();
		$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
		$table->timestamps();
	});
}

running seeds with truncate() will trigger a constraint violation if foreign key checks is not disabled.

	Syntax error or access violation: 1701 Cannot truncate a table referenced in a foreign key constraint ...

The fix:

DatabaseSeeder.php

class DatabaseSeeder extends Seeder {

	/**
	 * Run the database seeds.
 	 *
	 * @return void
	 */
	public function run()
	{
		Eloquent::unguard();

		//disable foreign key check for this connection before running seeders
		DB::statement('SET FOREIGN_KEY_CHECKS=0;');
			
		$this->call('UsersTableSeeder');
		$this->call('PostsTableSeeder');

		// supposed to only apply to a single connection and reset it's self
		// but I like to explicitly undo what I've done for clarity
		DB::statement('SET FOREIGN_KEY_CHECKS=1;');
		
	}

}

fix from here http://stackoverflow.com/questions/14666277/laravel-4-working-with-relationships-in-seeds

As pointed out in the comments at SO you wouldn't want to disable foreign key checks on a production app but you really don't want to run seed files in production either so obviously this is not intended for production but helpful in development.

@Amvos2000
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Thx this saved my project

@RyotaBannai
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@mikedamoiseau thank you!!

@edrisaturay
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Thanks for this fix. works on laravel 7

@pishguy
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pishguy commented May 29, 2020

you can use this code on Laravel 7

Schema::disableForeignKeyConstraints();

$this->call(UserTableSeeder::class);
$this->call(LanguageTableSeeder::class);

Schema::enableForeignKeyConstraints();

@henryavila
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Hi, I have this problem in MsSQL, and I conclude that I have just 2 options (beside moving away from MSSQL =D)

  1. Remove the foreign key, truncate and recreate the foreign key
  2. Delete table data and reset the Auto increment

I Found the approach 2 much better. Here is the working code:

$tableName = (new Model())->getTable();
\Illuminate\Support\Facades\DB::table($tableName )->delete();
\Illuminate\Support\Facades\DB::statement("DBCC CHECKIDENT ({$tableName }, RESEED, 0)");

Baiscally its what the truncate does (obviously the truncate is much faster), But it work.

@remusbejusca87
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thanks man, it worked for me!

@pankajToday
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j

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