INTRODUCTION
Database tables are often related to one another. For example, a blog post may have many comments, or an order could be related to the user who placed it. Eloquent makes managing and working with these relationships easy, and supports several different types of relationships:
DEFINING RELATIONSHIPS
Eloquent relationships are defined as methods on your Eloquent model classes. Since, like Eloquent models themselves, relationships also serve as powerful query builders, defining relationships as methods provides powerful method chaining and querying capabilities. For example, we may chain additional constraints on this posts relationship:
$user->posts()->where('active', 1)->get();But, before diving too deep into using relationships, let’s learn how to define each type.
#One To One
A one-to-one relationship is a very basic relation. For example, a User model might be associated with one Phone. To define this relationship, we place a phone method on the User model. The phone method should call the hasOne method and return its result:
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class User extends Model
{
/**
* Get the phone record associated with the user.
*/
public function phone()
{
return $this->hasOne('App\Phone');
}
}
Additionally, Eloquent assumes that the foreign key should have a value matching the id (or the custom $primaryKey) column of the parent. In other words, Eloquent will look for the value of the user's id column in the user_id column of the Phone record. If you would like the relationship to use a value other than id, you may pass a third argument to the hasOne method specifying your custom key:
return $this->hasOne('App\Phone', 'foreign_key', 'local_key');Defining The Inverse Of The Relationship
So, we can access the Phone model from our User. Now, let's define a relationship on the Phone model that will let us access the User that owns the phone. We can define the inverse of a hasOne relationship using the belongsTo method:
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Phone extends Model
{
/**
* Get the user that owns the phone.
*/
public function user()
{
return $this->belongsTo('App\User');
}
}
If your parent model does not use id as its primary key, or you wish to join the child model to a different column, you may pass a third argument to the belongsTo method specifying your parent table's custom key:
/**
* Get the user that owns the phone.
*/
public function user()
{
return $this->belongsTo('App\User', 'foreign_key', 'other_key');
}#One To Many
A one-to-many relationship is used to define relationships where a single model owns any amount of other models. For example, a blog post may have an infinite number of comments. Like all other Eloquent relationships, one-to-many relationships are defined by placing a function on your Eloquent 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('App\Comment');
}
}
Since all relationships also serve as query builders, you can add further constraints to which comments are retrieved by calling the comments method and continuing to chain conditions onto the query:
$comment = App\Post::find(1)->comments()->where('title', 'foo')->first();Like the hasOne method, you may also override the foreign and local keys by passing additional arguments to the hasMany method:
return $this->hasMany('App\Comment', 'foreign_key');
return $this->hasMany('App\Comment', 'foreign_key', 'local_key');#One To Many (Inverse)
Now that we can access all of a post’s comments, let’s define a relationship to allow a comment to access its parent post. To define the inverse of a hasMany relationship, define a relationship function on the child model which calls the belongsTo method:
<?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('App\Post');
}
}
If your parent model does not use id as its primary key, or you wish to join the child model to a different column, you may pass a third argument to the belongsTo method specifying your parent table's custom key:
/**
* Get the post that owns the comment.
*/
public function post()
{
return $this->belongsTo('App\Post', 'foreign_key', 'other_key');
}I Think That’s all about defining relationships what i know for more info u can click here : https://laravel.com/docs/7.x/eloquent-relationships
