How To Delete Multiple Data From Different Table - laravel

Question

I have two tables like this
Books
id|book_name|writter_id
1|Artemis|1
Writters
id|writter_name
1|Jane Doe
both of the tables have a relationship like this
Book model return $this->belongsTo('App\Writter', 'writter_id');
Writter model return $this->hasMany('App\Book', 'writter_id');
books.index.blade.php
<p>{{ $book->writter->writter_name }}</p>
create books
public function up()
{
Schema::create('books', function (Blueprint $table) {
$table->increments('id');
$table->string('book_name', 100)->unique();
$table->integer('writter_id')->unsigned();
$table->timestamps();
});
}
create writter
public function up()
{
Schema::create('writters', function (Blueprint $table) {
$table->increments('id');
$table->string('writter_name', 100);
$table->timestamps();
});
// Set Foreign Key
Schema::table('books', function (Blueprint $table) {
$table->foreign('writter_id')
->references('id')
->on('writers')
->onDelete('cascade')
->onUpdate('cascade');
});
}
/**
* Reverse the migrations.
*
* #return void
*/
public function down()
{
// Drop Foreign Key di kolom id_penulis di table books
Schema::table('books', function(Blueprint $table) {
$table->dropForeign('books_writter_id_foreign');
});
Schema::drop('writters');
}
Every time i delete the writters (for an example like jane doe above) the books data still have the writter_id So the index view throw me an error.
Is it possible to delete the data/row from the writters table, and delete the writter_id on the books in the same time?

Answer 1

Edit your books table migration and add foreign keys
$table->integer('writter_id')->unsigned()->nullable();
Schema::table('books', function($table) {
$table->foreign('writter_id')->references('id')->on('writters')->onDelete('set null');
});
As you see it sets null on writter delete

Answer 2

For make youre migration file, do you use foreign key ?
With foreign key you can add a method for on Delete.
Foreign key Documentation
migration.php
$table->integer('writter_id')->unsigned();
$table->foreign('writter_id)->references('id')->on('writters)->onDelete('cascade');
It's will be work

Answer 3

If you haven't set up foreign keys on your tables, removing a row from a table won't update the column referencing to that row.
To solve this we can set up foreign keys with the schema builder.
You can create a new migration file or modify your existing migrations if you don't care about your current database values.
Create a new migration file with php artisan make:migration. Inside that file, use these methods (don't forget to run composer require doctrine/dbal before running the migration):
public function up() {
// Remove current foreign keys and index.
Schema::table('books', function (Blueprint $table) {
$table->dropForeign('books_writter_id_foreign');
$table->dropIndex('books_writter_id_foreign');
});
// Add new foreign and allow books to now have a writter by using `NULL`.
Schema::table('books', function (Blueprint $table) {
$table->integer('writter_id')->unsigned()->nullable()->change(); // Before changing a column, be sure to add the doctrine/dbal dependency to your composer.json file.
$table->foreign('writter_id')
->references('id')
->on('writers')
->onDelete('SET NULL');
});
}
public function down() {
// Revert to previous values.
Schema::table('books', function (Blueprint $table) {
$table->dropForeign('books_writter_id_foreign');
$table->dropIndex('books_writter_id_foreign');
$table->integer('writter_id')->unsigned()->change();
$table->foreign('writter_id')
->references('id')
->on('writers')
->onDelete('cascade')
->onUpdate('cascade');
});
}
Using ->onDelete('SET NULL') on the foreign key will set the value to NULL when the referenced value is deleted from the referenced table.
In your blade file you can now check if the book have a writer before outputting it:
#if ($book->writter_id)
<p>{{ $book->writter->writter_name }}</p>
#endif