Laravel : Setup One to Many Eloquent Relationship Tutorial

Leave a Comment / By / Updated on April 2, 2023

In Laravel, the one-to-many eloquent relationship is a powerful feature that allows you to associate one database table with multiple tables. This means that a record in one table, can be linked to many records in another table.

In this tutorial, we will cover how to create a one-to-many eloquent relationship in Laravel, from creating migrations with foreign keys to retrieving and manipulating data.

 

What One to Many Eloquent Means?

In the context of the Laravel framework’s Eloquent ORM, a one-to-many relationship refers to a type of database relationship. A single record in one table can be associated with multiple records in another table.

For example, consider a scenario where you have two database tables named “users” and “posts”. Each user can create multiple posts, but each post is created by only one user. In this case, the “users” table has a one-to-many relationship with the “posts” table.

To establish a one-to-many relationship in Eloquent, you will define a “hasMany” relationship on the parent model and a “belongsTo” relationship on the child model. This will allow you to easily retrieve all the posts associated with a user, or retrieve the user who created a specific post.

Eloquent makes it easy to work with one-to-many relationships and provides many helpful methods for querying and managing related data.

 

How to Setup One to Many Eloquent Relationships in Laravel?

Follow these steps to creating setup one too many eloquent relationships:

  • Create Migrations
  • Create Models
  • Retrieve Records
  • Create Records
  • Delete Records
  • Sync with Pivot Table

 

Create Migrations

To create the posts and comments tables, we will use Laravel’s migration feature. We will first create the posts table, which has a primary key id, a name column, and timestamps:

Schema::create('posts', function (Blueprint $table) {

    $table->increments('id');
    $table->string("name");
    $table->timestamps();

});

Next, we will create the comments table, which has a primary key id, a comment column, post_id column as a foreign key referencing the id column of the posts table, and timestamps:

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');

});

The onDelete method specifies that if a post is deleted, all its comments should also be deleted. This is important for maintaining data integrity.

 

Create Models

After creating the migrations, we need to create models for the posts and comments tables. We will use Laravel’s Eloquent Model to create a relationship between the two tables.

Here is the code for the Post model:

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);
    }
}

The hasMany() method defines the relationship between the posts and comments tables. It means that a post can have many comments.

Here is the code for the Comment model:

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);
    }
}

The belongsTo() method defines the relationship between the comments and posts tables. It means that a comment belongs to a post.

 

Retrieve Records

After creating the models and migrations, we can now retrieve records from the database using the eloquent relationships.

Let’s say we want to retrieve all comments associated with a particular post. We can do this by finding the post by its id and accessing the comments using the comments() method that we defined in the Post model. Here’s an example:

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

In this example, we’re finding the post with an id of 1 and then accessing its comments using the comments() method. This will return a collection of all comments associated with the post.

We can also retrieve the post that a particular comment belongs to using the belongsTo() method that we defined in the Comment model. Here’s an example:

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

In this example, we’re finding the comment with an id of 1 and then accessing its post using the post() method. This will return the post that the comment belongs to.

These are just a few examples of how we can retrieve data using the one to many eloquent relationship in Laravel. We can also use methods like first(), get(), and where() to filter and retrieve specific records.

Let’s move on to updating the comments in the one-to-many relationship. To update the comment, we can simply retrieve the comment object and update the comment attribute. For example, let’s update the comment with id=1 and change the comment text to “Updated comment text”.

$comment = Comment::find(1);
$comment->comment = "Updated comment text";
$comment->save();

This will update the comment with id=1 and change its comment text to “Updated comment text”. Similarly, we can update all the comments in the same way.

 

Create Records

Creating new records for the one-to-many relationship in Laravel is a straightforward process. You can create a new Comment instance and save it to a Post model using the save method. Alternatively, you can use the saveMany method to save multiple comments at once.

To create a new Comment instance and save it to a Post model, you can follow the example code below:

$post = Post::find(1);

$comment = new Comment;
$comment->comment = "Hi there!";

$post = $post->comments()->save($comment);

In the example above, we first retrieve the Post model with an id of 1 using the find method. We then create a new Comment instance and set its comment attribute to “Hi there!”. Finally, we use the save method on the Post model’s comments relationship to save the new Comment instance to the database.

To save multiple comments at once, you can use the saveMany method. For example:

$post = Post::find(1);

$comment1 = new Comment;
$comment1->comment = "Hi Jolly Comment 1";

$comment2 = new Comment;
$comment2->comment = "Hi Jolly Comment 2";

$post = $post->comments()->saveMany([$comment1, $comment2]);

In this example, we create two new Comment instances and set their comment attributes to “Hi Jolly Comment 1” and “Hi Jolly Comment 2”, respectively. We then use the saveMany method on the Post model’s comments relationship to save both Comment instances to the database at once.

Now that we have created new records for the one-to-many relationship in Laravel, let’s move on to updating and deleting them.

 

Delete Records:

We can also delete the records in the one-to-many relationship. To delete a comment, we can retrieve the comment object and call the delete method on it. For example, let’s delete the comment with id=1.

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

This will delete the comment with id=1 from the database. Similarly, we can delete all the comments in the same way.

 

Sync with Pivot Table:

In the one-to-many relationship, we can also use a pivot table to associate multiple records with a single record. The pivot table is used to store the relationship between the two tables. In Laravel, we can use the sync method to sync the pivot table with the associated records.

Let’s say we have a tags table and we want to associate multiple tags with a post. We can create a pivot table called post_tag with columns post_id and tag_id. Then we can use the sync method to sync the pivot table with the associated tags.

class Post extends Model
{
    /**
     * The tags that belong to the post.
     */
    public function tags()
    {
        return $this->belongsToMany(Tag::class);
    }
}

class Tag extends Model
{
    /**
     * The posts that belong to the tag.
     */
    public function posts()
    {
        return $this->belongsToMany(Post::class);
    }
}

// Sync tags with post
$post = Post::find(1);
$post->tags()->sync([1, 2, 3]);

This will sync the pivot table post_tag with the post and tags.

 

 

FAQs:

 

What is a one-to-many relationship in Laravel?

A one-to-many relationship in Laravel is used when one table is associated with multiple tables.

 

What is the difference between hasMany() and belongsTo() in Laravel?

hasMany() is used to define a one-to-many relationship from the parent model to the child model, while belongsTo() is used to define a one-to-many relationship from the child model to the parent model.

 

How to create a migration with a foreign key schema in Laravel?

To create a migration with a foreign key schema in Laravel, you can use the foreign() method to define a foreign key constraint.

 

How to retrieve records in a one-to-many relationship in Laravel?

To retrieve records in a one-to-many relationship in Laravel, you can use the hasMany() method to retrieve all the child records associated with the parent record.

 

Conclusion:

In this tutorial, we have learned how to create a one-to-many relationship in Laravel using the Eloquent Model. We have covered everything related to one-to-many relationships, including creating migrations with foreign key schema, creating models with hasMany() and belongsTo() relationships, retrieving records, creating records, updating records, deleting records, and syncing with a pivot table. I hope this tutorial will help you in understanding one-to-many relationships in Laravel.

Category: Laravel

Leave a Comment

Your email address will not be published. Required fields are marked *