How To Create a One To Many Relationship in Laravel 9?

Hi friends,

Today I explain how to create a one to many relationship in laravel 9. so now in this tutorial i will show you laravel 9 one to many eloquent relationship. When one table refers to many rows in another table that is called a one-to-many relationship. A one-to-many relationship is a very basic type of database relationship in laravel 9.

Using one to many relationship, you can perform crud (create, read, update, delete) operation with the eloquent model from the database table in laravel 9.

So let's start following example:

Step 1: Download Laravel

Let us begin the tutorial by installing a new laravel application. if you have already created the project, then skip following step.

composer create-project laravel/laravel example-app

Step 2: Add Migrations

Now we have to create migration of "posts" and "comments" table. we will also add foreign key with posts table. so let's create like as below:

php artisan make:migration create_posts_table

database\migrations\2014_10_12_000000_create_posts_table

<?php
  
use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;
  
return new class extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->id();
            $table->string("name");
            $table->timestamps();
        });
    }
  
    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('posts');
    }
};

comments table migration:

php artisan make:migration create_comments_table

database\migrations\2014_10_12_000000_create_comments_table

<?php
  
use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;
  
return new class extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('comments', function (Blueprint $table) {
            $table->id();
            $table->foreignId('post_id')->constrained('posts');
            $table->string("comment");
            $table->timestamps();
        });
    }
  
    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('comments');
    }
};

Step 3: Add Models

Here, we will create Post and Comment table model. we will also use "hasMany()" and "belongsTo()" for relationship of both model.

php artisan make:model Post

app/Models/Post.php

<?php
  
namespace App\Models;
  
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
  
class Post extends Model
{
    use HasFactory;
 
    /**
     * Get the comments for the blog post.
     *   
     * Syntax: return $this->hasMany(Comment::class, 'foreign_key', 'local_key');
     *
     * Example: return $this->hasMany(Comment::class, 'post_id', 'id');
     * 
     */
    public function comments()
    {
        return $this->hasMany(Comment::class);
    }
}

Comment Model:

php artisan make:model Comment

app/Models/Comment.php

<?php
  
namespace App\Models;
  
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
  
class Comment extends Model
{
    use HasFactory;
  
    /**
     * Get the post that owns the comment.
     *  
     * Syntax: return $this->belongsTo(Post::class, 'foreign_key', 'owner_key');
     *
     * Example: return $this->belongsTo(Post::class, 'post_id', 'id');
     * 
     */
    public function post()
    {
        return $this->belongsTo(Post::class);
    }
}

Step 4: Retrieve Records:

php artisan make:controller PostController

app/Http/Controllers/PostController.php

<?php
  
namespace App\Http\Controllers;
  
use Illuminate\Http\Request;
use App\Models\Post;
  
class PostController extends Controller
{
    /**
     * Write code on Method
     *
     * @return response()
     */
    public function index(Request $request)
    {
        $comments = Post::find(1)->comments;
  
        dd($comments);
    }
}

app/Http/Controllers/PostController.php

<?php
 
namespace App\Http\Controllers;
  
use Illuminate\Http\Request;
use App\Models\Comment;
  
class PostController extends Controller
{
    /**
     * Write code on Method
     *
     * @return response()
     */
    public function index(Request $request)
    {
        $post = Comment::find(1)->post;
  
        dd($post);
    }
}

Step 5: Add Records:

app/Http/Controllers/PostController.php

<?php
  
namespace App\Http\Controllers;
  
use Illuminate\Http\Request;
use App\Models\Post;
use App\Models\Comment;
  
class PostController extends Controller
{
    /**
     * Write code on Method
     *
     * @return response()
     */
    public function index(Request $request)
    {
        $post = Post::find(1);
   
        $comment = new Comment;
        $comment->comment = "Hi ItSolutionStuff.com";
           
        $post = $post->comments()->save($comment);
    }
}

app/Http/Controllers/PostController.php

<?php
  
namespace App\Http\Controllers;
   
use Illuminate\Http\Request;
use App\Models\Post;
use App\Models\Comment;
  
class PostController extends Controller
{
    /**
     * Write code on Method
     *
     * @return response()
     */
    public function index(Request $request)
    {
        $post = Post::find(1);
   
        $comment1 = new Comment;
        $comment1->comment = "Hi ItSolutionStuff.com Comment 1";
           
        $comment2 = new Comment;
        $comment2->comment = "Hi ItSolutionStuff.com Comment 2";
           
        $post = $post->comments()->saveMany([$comment1, $comment2]);
    }
}

app/Http/Controllers/PostController.php

<?php
   
namespace App\Http\Controllers;
  
use Illuminate\Http\Request;
use App\Models\Post;
use App\Models\Comment;
  
class PostController extends Controller
{
    /**
     * Write code on Method
     *
     * @return response()
     */
    public function index(Request $request)
    {
        $comment = Comment::find(1);
        $post = Post::find(2);
           
        $comment->post()->associate($post)->save();
    }
}

I hope it will help you..