When one table is linked to numerous tables, a one-to-many relationship is used. A post, for example, could include many comments. In the examples of Laravel 6, Laravel 7, Laravel 8, and Laravel 9, there is an eloquent one-to-many relationship.
So, in this tutorial, you'll learn how to establish a one-to-many relationship migration using a foreign key schema, how to utilise sync with a pivot table, how to add records, obtain all data, delete, update, and everything else related to one-to-many relationships.
I'll make a "posts" table and a "comments" table in this example. Both tables are linked to one another. Using the Laravel Eloquent Model, we'll now construct one-to-many relationships with each other. We'll start with database migration, then move on to modeling, retrieving records, and finally creating records. 

"hasMany()" and "belongsTo()" will be used for relation in a One to Many Relationship.

1. Create Migrations

The "posts" and "comments" tables must now be migrated. With the posts table, we'll also add a foreign key. So, let's make something like this:

Posts table migration

Schema::create('posts', function (Blueprint $table) {
    $table->increments('id');
    $table->string("name");
    $table->timestamps();
});

Comments table migration

Schema::create('comments', function (Blueprint $table) {
    $table->increments('id');
    $table->integer('post_id')->unsigned();
    $table->string("comment");
    $table->timestamps();
    $table->foreign('post_id')->references('id')->on('posts')
        ->onDelete('cascade');
});

2. Create Models

We'll make a Post and Comment table model here. For both models' relationships, we'll use "hasMany()" and "belongsTo()."

Post Model

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Post extends Model
{
    /**
     * Get the comments for the blog post.
     */
    public function comments()
    {
        return $this->hasMany(Comment::class);
    }
}
?>

Comment Model

<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Comment extends Model
{
    /**
     * Get the post that owns the comment.
     */
    public function post()
    {
        return $this->belongsTo(Post::class);
    }
}
?>

3. Retrieve Records

$post = Post::find(1);
$comments = $post->comments;
dd($comments);

$comment = Comment::find(1);
$post = $comment->post;
dd($post);

4. Create Records

$post = Post::find(1);
$comment = new Comment;
$comment->comment = "Hi CodeSolutionStuff";
$post = $post->comments()->save($comment);

$post = Post::find(1);
$comment1 = new Comment;
$comment1->comment = "Hi CodeSolutionStuff Comment 1";
$comment2 = new Comment;
$comment2->comment = "Hi CodeSolutionStuff Comment 2";
$post = $post->comments()->saveMany([$comment1, $comment2]);

$comment = Comment::find(1);
$post = Post::find(2);
$comment->post()->associate($post)->save();

I hope you will like the content and it will help you to learn Laravel One to Many Eloquent Relationship
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