How to delete a foreign key constraint in Laravel? - php

Question

I'm working on a project in which I' m adding data in two tables User & Registration in one form like this
public function storeStudent(Request $request)
{
$created_user = User::create([
'name' => $request->name,
'email' => $request->email,
'password' => bcrypt($request->password),
'parent_id' => $request->parent_id,
'role_id' => $request->role_id,
'gender'=> $request->gender,
'date_of_birth'=> $request->date_of_birth,
'cnic'=>$request->cnic,
'religion'=>$request->religion,
'skills'=>$request->skills,
'physical'=>$request->physical,
'emergency_name'=>$request->emergency_name,
'phone_no'=>$request->phone_no,
'medical_info'=>$request->medical_info,
'family_dr'=>$request->family_dr,
'address'=>$request->address,
]);
Registration::create([
//reg_id is id for registration table
'user_id' => $created_user->id,
'class_id' => $request->class_id,
'section_id' => $request->section_id,
]);
Now I want to delete the data I'm bad with syntaxes. I don't know what should I do to delete the data I m trying
public function destroy(Request $request)
{
$user = User::findOrFail($request->user_id);
$user->delete();
$registration=Registration::findOrFail($request->user_id);
$registration->delete();
return back();
}
Table for Registration is
Schema::create('registrations', function (Blueprint $table) {
$table->increments('reg_id');
$table->integer('user_id')->unsigned();
$table->foreign('user_id')->references('id')->on('users');
$table->integer('class_id')->unsigned();
$table->foreign('class_id')->references('id')->on('classses');
$table->integer('section_id')->unsigned();
$table->foreign('section_id')->references('id')->on('sections');
$table->timestamps();
});
But it gives me error
Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails (`jurs1`.`registrations`, CONSTRAINT `registrations_user_id_foreign` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`)) (SQL: delete from `users` where `id` = 10)
Please help me in this case.

Answer 1

$table->integer('user_id')->unsigned();
$table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
Using ->onDelete('cascade') works for me :)

Answer 2

You cannot delete a record from the user table because you have a relationship with the registrations table (registrations_user_id_foreign). In order to delete a user record, you first have to delete all the records for that user from the registrations table. You have two ways:
Modify the relationships of your registrations table
$table->foreign('user_id')->references ('id')->on('users')->onDelete ('cascade');
With this, when you do a
$user->delete()
the records of that user will be deleted from the registrations table too.
Or second way:
Delete user after deleting registrations records
$user->registrations()->delete();
$user->delete();

Answer 3

In Laravel 9 you can use detach method:
$user->registrations()->detach();
$user->delete();