How to Use hasOne Relationship in Laravel with Example ?

hasOne relationship in laravel is used to create the relation between two tables. hasOne means create the relation one to one. For example if a article has comments and we wanted to get one comment with the article details then we can use hasOne relationship or a user can have a profile table.

Database Relations are used to create the relations between the tables so that we can manage the transactions in a better way. Similar to database relations laravel itself provides relationships out of the box to create the relation between tables in the application layer.

Laravel relations do not create relations in database it creates relation in application layer and produces the output.

Laravel eloquent hasOne accepts 3 parameters first as model name, second is optional foreign_key and third is optional local_key .

Here is the syntax

<?php
 
namespace App\Models;
 
use Illuminate\Database\Eloquent\Model;
 
class Owner extends Model
{
     
    public function child()
    {
        return $this->hasOne(child::class,'foreign_key','local_key');
    }
}

In the above syntax we have used belongsTo method with 3 parameters so here Child::class is the name of Model which we want to relate, foreign_key means column name of child table and local_key means column name of own table.

Laravel do not create join query internally but it creates a separate query and then attach the data.

So we can use it as below:

Article::with('child')->get();

This will return all the articles along with first comment.

Let’s understand laravel hasOne in eloquent query with example

Use of hasOne to method in article comments table

Suppose we have two tables one is article and another one is comments so comments table contains comments of articles table so here is the schema of both tables and you can also read How to make database connection in Laravel 8 ?

Step 1 : Create article and comment model

Create two model in app\Models folder, one is article and other is comment

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Article extends Model
{
    use HasFactory;
}

Comment Model:

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Comment extends Model
{
    use HasFactory;
}

Step 2 : Create hasOne relation in Article model

Now create hasOne relation in Article class so that we can fetch comment detail using article_id

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;

class Article extends Model
{
    use HasFactory;

    public function comment(){
        return $this->hasOne(Comment::class);
    }
}

In the above code we have created a method comment and used hasOne method to create the relation with Comment Model.

Laravel assumes here table name is comment and foreign key is comments table article_id and local key is articles table id. If you have different columns name to map then you can change.

Step 3 : Use the relationship in controller

We have created the relation now we need to access the model and its relations so lets create a controller and import the necessary classes

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use App\Models\Article;


class ArticleController extends Controller
{

    public function index(Request $request)
    {

        $article=Article::with("comment")->first();
        dump($article);

        dump($article->comment);

    }
}

Step 4 : Create Route

Lastly create the route in web.php

Route::get('/articles',[ArticleController::class, 'index']); 

How to get last row relation in hasOne relation ?

Sometime we wanted to get last row in hasOne relation so then we can use oldestOfMany method

public function comment(){
        return $this->hasOne(Comment::class)-> oldestOfMany();
}

How to get last first relation in hasOne relation ?

Sometime we wanted to get first row in hasOne relation so then we can use lastestOfMany method

public function comment(){
        return $this->hasOne(Comment::class)->lastestOfMany();
}