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How can you retrieve data from a one-to-many relationship in Laravel?

Published at
9/18/2023
Categories
laravel10
eloquent
relationships
howto
Author
devmahmoudadel
Main Article
https://dev.to/devmahmoudadel/how-can-you-retrieve-data-from-a-one-to-many-relationship-in-laravel-2774
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How can you retrieve data from a one-to-many relationship in Laravel?

We saw how data is saved in multiple different ways within the database using the One-To-Many relationship in Laravel.
But how to fetch data from the database?
There are several ways in which data can be fetched from a database.
These methods are divided into two basic methods:

Through the user User Model

This method is divided into two sub-methods depending on how the data is organized after it is fetched from the data base

Without using API Resources.

1- We go first to the routes/web.php file so that we can test these methods and make the following modifications.

use App\Models\User;
---
Route::get('/users', function () {
    $users = User::with(['profile', 'posts'])->get();
    return view('users.list', compact('users'));
});
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Here we can choose the columns for each relationship as follows.

use App\Models\User;
---
Route::get('/users', function () {
    $users = User::with(['profile:id,firstname,lastname,user_id', 'posts:title,user_id'])->get();
    return view('users.list', compact('users'));
});
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In order to know the difference between selecting or not selecting columns from the database, let us see the specific response to each case.

  • In the first case, with all data retrieved without exception, we find that $users contains that data. 
[
  {
    "id": 1,
    "username": "John Doe",
    "created_at": "2023-08-07T06:23:03.000000Z",
    "updated_at": "2023-08-07T06:23:03.000000Z",
    "profile": {
      "id": 1,
      "firstname": "John",
      "lastname": "Doe",
      "birthday": "08-11-1991",
      "user_id": 1,
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    },
    "posts": [
      {
        "id": 1,
        "title": "Post title 1",
        "body": "Post body 1",
        "user_id": 1,
        "created_at": "2023-08-07T06:23:41.000000Z",
        "updated_at": "2023-08-07T06:23:41.000000Z"
      },
      {
        "id": 5,
        "title": "Post title 5",
        "body": "Post body 5",
        "user_id": 1,
        "created_at": "2023-08-07T06:23:41.000000Z",
        "updated_at": "2023-08-07T06:23:41.000000Z"
      },
      {
        "id": 6,
        "title": "Post title 6",
        "body": "Post body 6",
        "user_id": 1,
        "created_at": "2023-08-07T06:23:41.000000Z",
        "updated_at": "2023-08-07T06:23:41.000000Z"
      }
    ]
  },
  {
    "id": 2,
    "username": "Tom Cruz",
    "created_at": "2023-08-07T06:23:03.000000Z",
    "updated_at": "2023-08-07T06:23:03.000000Z",
    "profile": {
      "id": 2,
      "firstname": "Tom",
      "lastname": "Cruz",
      "birthday": "01-02-2000",
      "user_id": 2,
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    },
    "posts": [
      {
        "id": 2,
        "title": "Post title 2",
        "body": "Post body 2",
        "user_id": 2,
        "created_at": null,
        "updated_at": null
      },
      {
        "id": 3,
        "title": "Post title 3",
        "body": "Post body 3",
        "user_id": 2,
        "created_at": null,
        "updated_at": null
      },
      {
        "id": 7,
        "title": "Post title 7",
        "body": "Post body 7",
        "user_id": 2,
        "created_at": "2023-08-07T06:23:41.000000Z",
        "updated_at": "2023-08-07T06:23:41.000000Z"
      }
    ]
  },
  {
    "id": 3,
    "username": "Adam Smith",
    "created_at": "2023-08-07T06:23:03.000000Z",
    "updated_at": "2023-08-07T06:23:03.000000Z",
    "profile": {
      "id": 3,
      "firstname": "Adam",
      "lastname": "Smith",
      "birthday": "01-01-1999",
      "user_id": 3,
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    },
    "posts": [
      {
        "id": 4,
        "title": "Post title 4",
        "body": "Post body 4",
        "user_id": 3,
        "created_at": "2023-08-07T06:23:41.000000Z",
        "updated_at": "2023-08-07T06:23:41.000000Z"
      }
    ]
  }
]
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  • In the second case, when specifying the exact required columns from the database, we find that the response is as follows. 
[
  {
    "id": 1,
    "username": "John Doe",
    "created_at": "2023-08-07T06:23:03.000000Z",
    "updated_at": "2023-08-07T06:23:03.000000Z",
    "profile": {
      "id": 1,
      "firstname": "John",
      "lastname": "Doe",
      "user_id": 1
    },
    "posts": [
      {
        "title": "Post title 1",
        "user_id": 1
      },
      {
        "title": "Post title 5",
        "user_id": 1
      },
      {
        "title": "Post title 6",
        "user_id": 1
      }
    ]
  },
  {
    "id": 2,
    "username": "Tom Cruz",
    "created_at": "2023-08-07T06:23:03.000000Z",
    "updated_at": "2023-08-07T06:23:03.000000Z",
    "profile": {
      "id": 2,
      "firstname": "Tom",
      "lastname": "Cruz",
      "user_id": 2
    },
    "posts": [
      {
        "title": "Post title 2",
        "user_id": 2
      },
      {
        "title": "Post title 3",
        "user_id": 2
      },
      {
        "title": "Post title 7",
        "user_id": 2
      }
    ]
  },
  {
    "id": 3,
    "username": "Adam Smith",
    "created_at": "2023-08-07T06:23:03.000000Z",
    "updated_at": "2023-08-07T06:23:03.000000Z",
    "profile": {
      "id": 3,
      "firstname": "Adam",
      "lastname": "Smith",
      "user_id": 3
    },
    "posts": [
      {
        "title": "Post title 4",
        "user_id": 3
      }
    ]
  }
]
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Here we see the difference between the two cases in the size of the data that was processed, and the matter increases if the size of the data is much larger than that.
When selecting specific columns in relationships, you must choose foreignKey because without choosing it, the data will not be returned correctly from the database.

2- We go to the following path resources/views/users and modify this file list.blade.php to display the users and their profiles. Also, what interests us here is displaying the posts for each user.

<table>
    <thead>
        <tr>
            <th style="text-align: center">Username</th>
            <th style="text-align: center">Firstname</th>
            <th style="text-align: center">Lastname</th>
            <th style="text-align: center">Posts</th>
        </tr>
    </thead>
    <tbody>
        @foreach ($users as $user)
            <tr>
                <td>{{ $user->username }}</td>
                <td>{{ $user->profile->firstname }}</td>
                <td>{{ $user->profile->lastname }}</td>
                <td>
                    <ul>
                        @foreach ($user->posts as $post)
                            <li>{{ $post->title }}</li>
                        @endforeach
                    </ul>
                </td>
            </tr>
        @endforeach
    </tbody>
</table>
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3- Open the browser and go to the following link http://127.0.0.1:8000/users to see what results will appear.
Users view with posts

By using API Resources.

1- We will create an API Resource for the Post form by executing this command in the command prompt.

php artisan make:resource PostResource
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2- You go to the following path App/Http/Resources and we begin to modify each of the following:

  • PostResource.php. 
<?php

namespace App\Http\Resources;

use Illuminate\Http\Request;
use Illuminate\Http\Resources\Json\JsonResource;

class PostResource extends JsonResource
{
    public function toArray(Request $request): array
    {
        return [
            'id' => $this->id,
            'title' => $this->title,
            'body' => $this->body,
        ];
    }
}
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3- We first go to the routes/api.php file to add a new route.

use App\Models\User;
use App\Http\Resources\UserResource;
---
Route::get('/users', function () {
    $users = User::with(['profile', 'posts'])->get();
    $usersResource = UserResource::collection($users);
    return response()->json($usersResource);
});
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4- Open the browser and go to the following link http://127.0.0.1:8000/api/users to see what results will appear.

[
  {
    "id": 1,
    "username": "John Doe",
    "profile": {
      "id": 1,
      "firstname": "John",
      "lastname": "Doe"
    },
    "postss": [
      {
        "user_id": 1,
        "title": "Post title 1"
      },
      {
        "user_id": 1,
        "title": "Post title 5"
      },
      {
        "user_id": 1,
        "title": "Post title 6"
      }
    ]
  },
  {
    "id": 2,
    "username": "Tom Cruz",
    "profile": {
      "id": 2,
      "firstname": "Tom",
      "lastname": "Cruz"
    },
    "postss": [
      {
        "user_id": 2,
        "title": "Post title 2"
      },
      {
        "user_id": 2,
        "title": "Post title 3"
      },
      {
        "user_id": 2,
        "title": "Post title 7"
      }
    ]
  },
  {
    "id": 3,
    "username": "Adam Smith",
    "profile": {
      "id": 3,
      "firstname": "Adam",
      "lastname": "Smith"
    },
    "postss": [
      {
        "user_id": 3,
        "title": "Post title 4"
      }
    ]
  }
]
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We also see here that we fetch only the required data.

Through the post Post Model

This method is divided into two sub-methods depending on how the data is organized after it is fetched from the data base

Without using API Resources.

1- We first go to the routes/web.php file so that we can test these methods and add this new route.

use App\Models\Post;
---
Route::get('/posts', function () {
    $posts = Post::with('user', 'user.profile')->get();
    return view('posts.list', compact('posts'));
});
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Here we can choose the columns for each relationship as follows.

use App\Models\Post;
---
Route::get('/posts', function () {
    $posts = Post::with('user:username,id', 'user.profile:firstname,lastname,user_id')->get();
    return view('posts.list', compact('posts'));
});
Enter fullscreen mode Exit fullscreen mode

In order to know the difference between selecting or not selecting columns from the database, let us see the specific response to each case.

  • In the first case, with all data retrieved without exception, we find that $posts contains that data. 
[
  {
    "id": 1,
    "title": "Post title 1",
    "body": "Post body 1",
    "user_id": 1,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "id": 1,
      "username": "John Doe",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  },
  {
    "id": 2,
    "title": "Post title 2",
    "body": "Post body 2",
    "user_id": 2,
    "created_at": null,
    "updated_at": null,
    "user": {
      "id": 2,
      "username": "Tom Cruz",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  },
  {
    "id": 3,
    "title": "Post title 3",
    "body": "Post body 3",
    "user_id": 2,
    "created_at": null,
    "updated_at": null,
    "user": {
      "id": 2,
      "username": "Tom Cruz",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  },
  {
    "id": 4,
    "title": "Post title 4",
    "body": "Post body 4",
    "user_id": 3,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "id": 3,
      "username": "Adam Smith",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  },
  {
    "id": 5,
    "title": "Post title 5",
    "body": "Post body 5",
    "user_id": 1,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "id": 1,
      "username": "John Doe",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  },
  {
    "id": 6,
    "title": "Post title 6",
    "body": "Post body 6",
    "user_id": 1,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "id": 1,
      "username": "John Doe",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  },
  {
    "id": 7,
    "title": "Post title 7",
    "body": "Post body 7",
    "user_id": 2,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "id": 2,
      "username": "Tom Cruz",
      "created_at": "2023-08-07T06:23:03.000000Z",
      "updated_at": "2023-08-07T06:23:03.000000Z"
    }
  }
]
Enter fullscreen mode Exit fullscreen mode
  • In the second case, when specifying the exact required columns from the database, we find that the response is as follows. 
[
  {
    "id": 1,
    "title": "Post title 1",
    "body": "Post body 1",
    "user_id": 1,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "username": "John Doe",
      "id": 1,
      "profile": {
        "firstname": "John",
        "lastname": "Doe",
        "user_id": 1
      }
    }
  },
  {
    "id": 2,
    "title": "Post title 2",
    "body": "Post body 2",
    "user_id": 2,
    "created_at": null,
    "updated_at": null,
    "user": {
      "username": "Tom Cruz",
      "id": 2,
      "profile": {
        "firstname": "Tom",
        "lastname": "Cruz",
        "user_id": 2
      }
    }
  },
  {
    "id": 3,
    "title": "Post title 3",
    "body": "Post body 3",
    "user_id": 2,
    "created_at": null,
    "updated_at": null,
    "user": {
      "username": "Tom Cruz",
      "id": 2,
      "profile": {
        "firstname": "Tom",
        "lastname": "Cruz",
        "user_id": 2
      }
    }
  },
  {
    "id": 4,
    "title": "Post title 4",
    "body": "Post body 4",
    "user_id": 3,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "username": "Adam Smith",
      "id": 3,
      "profile": {
        "firstname": "Adam",
        "lastname": "Smith",
        "user_id": 3
      }
    }
  },
  {
    "id": 5,
    "title": "Post title 5",
    "body": "Post body 5",
    "user_id": 1,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "username": "John Doe",
      "id": 1,
      "profile": {
        "firstname": "John",
        "lastname": "Doe",
        "user_id": 1
      }
    }
  },
  {
    "id": 6,
    "title": "Post title 6",
    "body": "Post body 6",
    "user_id": 1,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "username": "John Doe",
      "id": 1,
      "profile": {
        "firstname": "John",
        "lastname": "Doe",
        "user_id": 1
      }
    }
  },
  {
    "id": 7,
    "title": "Post title 7",
    "body": "Post body 7",
    "user_id": 2,
    "created_at": "2023-08-07T06:23:41.000000Z",
    "updated_at": "2023-08-07T06:23:41.000000Z",
    "user": {
      "username": "Tom Cruz",
      "id": 2,
      "profile": {
        "firstname": "Tom",
        "lastname": "Cruz",
        "user_id": 2
      }
    }
  }
]
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When choosing specific columns in the relationships, you must choose id and you must choose the user relationship, because without you choosing it, the user will not return with the post.

2- We go to the following path resources/views/users and modify this file list.blade.php to display the users and their profiles. Also, what interests us here is displaying the posts Private for each user.

<table>
    <thead>
        <tr>
            <th style="text-align: center">Username</th>
            <th style="text-align: center">Firstname</th>
            <th style="text-align: center">Lastname</th>
            <th style="text-align: center">Posts</th>
        </tr>
    </thead>
    <tbody>
        @foreach ($users as $user)
            <tr>
                <td>{{ $user->username }}</td>
                <td>{{ $user->profile->firstname }}</td>
                <td>{{ $user->profile->lastname }}</td>
                <td>
                    <ul>
                        @foreach ($user->posts as $post)
                            <li>{{ $post->title }}</li>
                        @endforeach
                    </ul>
                </td>
            </tr>
        @endforeach
    </tbody>
</table>
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3- Open the browser and go to the following link http://127.0.0.1:8000/users to see what results will appear.
Users view with posts

By using API Resources.

1- You go to the following path App/Http/Resources and we start editing the file PostResource.php:

<?php

namespace App\Http\Resources;

use Illuminate\Http\Request;
use Illuminate\Http\Resources\Json\JsonResource;

class PostResource extends JsonResource
{
    public function toArray(Request $request): array
    {
        return [
            'id' => $this->id,
            'title' => $this->title,
            'body' => $this->body,
            'user' => UserResource::make($this->whenLoaded('user')),
        ];
    }
}
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2- We first go to the routes/web.php file to add a new route.

use App\Models\Post;
use App\Http\Resources\PostResource;
---
Route::get('/posts', function () {
    $posts = Post::with(['user'])->get();
    $postsResource = PostResource::collection($posts);
    return response()->json($postsResource);
});
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3- Open the browser and go to the following link http://127.0.0.1:8000/api/posts to see what results will appear.

[
  {
    "id": 3,
    "title": "Post title 3",
    "body": "Post body 3",
    "user": {
      "id": 2,
      "username": "Tom Cruz"
    }
  },
  {
    "id": 4,
    "title": "Post title 4",
    "body": "Post body 4",
    "user": {
      "id": 3,
      "username": "Adam Smith"
    }
  },
  {
    "id": 5,
    "title": "Post title 5",
    "body": "Post body 5",
    "user": {
      "id": 1,
      "username": "John Doe Updated"
    }
  },
  {
    "id": 6,
    "title": "Post title 6",
    "body": "Post body 6",
    "user": {
      "id": 1,
      "username": "John Doe Updated"
    }
  },
  {
    "id": 7,
    "title": "Post title 7",
    "body": "Post body 7",
    "user": {
      "id": 2,
      "username": "Tom Cruz"
    }
  }
]
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We also see here that we fetch only the required data.

  • You can find the repo of this series on github here
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