Laravel Eloquent truncate - Foreign key constraint

Question

I am having some issues with deleting data using Laravel 5. I seem to be stuck on a 'foreign key constraint', while I don't see why.

In my current database model I have a datapoints table, which has a foreign key to the sensors table (datapoints.sensors_id -> sensor.id).

The code I am trying:

Route::get('/truncateData', function() {     DB::table('datapoints')->truncate();     DB::table('sensors')->truncate();     return 'Done...'; }); 

The result:

SQLSTATE[42000]: Syntax error or access violation: 1701 Cannot truncate a table referenced in a foreign key constraint (alerting.datapoints, CONSTRAINT datapoints_sensor_id_foreign FOREIGN KEY (sensor_id) REFERENCES alerting.sensors (id)) (SQL: truncate sensors)

I would understand this constraint if the order would be inverse (first deleting sensors), but when datapoints is empty, there should be no problem deleting sensors? I have also tried:

DB::table('datapoints')->delete(); DB::table('sensors')->delete(); return 'Done...'; 

Lastly I also tried adding explicitly 'DB::commit()' between the delete statements, but all return the same result.

Is this normal behaviour? Am I missing something?

Answer 1

No, this is the way your database works. You can't truncate table that is referenced by some other table. You may do something like

DB::statement('SET FOREIGN_KEY_CHECKS=0;'); DB::table('datapoints')->truncate(); DB::table('sensors')->truncate(); DB::statement('SET FOREIGN_KEY_CHECKS=1;'); 

to disable foreign key checks, truncate tables and enable it again.

Answer 2

If you prefer to use Eloquent objects, Maksym's answer the "Eloquent" way

use Illuminate\Support\Facades\Schema; use App\Models\Datapoint; use App\Models\Sensor;   Schema::disableForeignKeyConstraints(); Datapoint::truncate(); Sensor::truncate(); Schema::enableForeignKeyConstraints();