Introduction
Laravel comes with many feature sets through Eloquent ORM to get related data from database. Some are very easy and straightforward, like one-to-one and one-to-many, while some are complex in nature, like many-to-many and has many through. Thanks to laravel, even these complex relations seems piece of cake, when it comes to get as well as when we need to store such related data. However, as like anything else, it also have some limitations and we need to look for some alternative or workaround to achieve our goal.
One of limitation we are going to discuss in this article is – sorting data by pivot table when using many-to-many relation ship. So for that, let’s briefly understand what is pivot table in many-to-many relationship and then we will look into limitations of it and will give some workaround for the same.
What is Pivot Table?
The pivot table in laravel is a structured value that is grouped and aggregated in the individual items where the extensive table is obtained or accessed in the form of a spreadsheet, database, or other discrete functions. The summary and other functions in the pivot table include other statistical functions, sum, and average, where the groups of a pivot table are chosen, and the aggregate function is implied to grouped values. The field is created, and it is displayed on the right end of the worksheet, and the design and layout of the pivot table appear in the list by default. These fields in the pivot table are the building blocks of the pivot tables where all the fields in the list can be put into the layout with four unique options: rows, values, filters, and columns.
Example of PIvot table
In official documentation, they show the example of User-Role relationships, where the user potentially can belong to several roles and vice versa. So, for convenience to all, let’s consider this example only to head towards our problem statement.
Just to recall it, it would have a table structure something like this
users
id - integer
name - string
roles
id - integer
name - string
role_user
user_id - integer
role_id - integer
Here ‘role_user’ is our pivot table which will connect both of our table (‘users’ and ‘roles’) to form a many-to-many relationship between them.
The Problem – Sorting with Pivot Table
Let’s take the above example a bit further. Consider that our pivot table has an additional column called ‘role_assigned_at’ that stores the timestamp when a role is assigned to a user. We will consider unix timestamp over actual date-time to understand it briefly and clearly. So revised table structure will be something like this.
role_user
user_id - integer
role_id - integer
role_assigned_at - integer
Now, let’s assume we want to retrieve data of user’s roles, sorted by when role is assigned to user and in descending order
Laravel’s Eloquent ORM doesn’t directly support ordering by pivot table data out of the box. However, you can achieve this by using a combination of query builder methods and raw SQL expressions. Let’s see how you can do it.
Solution
Assuming we have a many-to-many relationship between two models, User and Role with a pivot table role_user, and we want to order users by a column – role_assigned_at in the pivot table, first we need to adjust relationships in our models.
// User.php
public function roles()
{
return $this->belongsToMany(Role::class)
->withPivot('role_assigned_at');
}
// Role.php
public function users()
{
return $this->belongsToMany(User::class)
->withPivot('role_assigned_at');
Now, use the relationship and the query builder to order by the pivot column – role_assigned_at
$sortedUsers = User::with(['roles' => function ($query) {
$query->orderBy('role_assigned_at', 'desc');
}])->get();
In the above example, we’re eager loading the roles relationship and using a closure to modify the query for ordering by the pivot column.
If you want to order by a pivot column of a related model, you’ll need to use a raw SQL expression. Here’s an example
$sortedUsers = User::with(['roles' => function ($query) {
$query->orderByRaw('(SELECT role_assigned_at FROM role_user WHERE role_user.role_id = roles.id) DESC');
}])->get();
In this case, we’re using a raw SQL subquery within the orderByRaw method to order the roles based on the pivot column value.
Keep in mind that using raw SQL expressions like this might make your code less portable across different database systems. Also, it’s important to ensure proper validation and sanitation of user inputs to prevent SQL injection vulnerabilities when using raw expressions.
Conclusion
As mentioned, all features may mostly have some or the other limitations. Some issues are very rare and minimal use case specific. However, sorting data by pivot table is something that most of us came across while using and going only a few steps ahead with many-to-many relationships. We hope that in upcoming versions of laravel, we will have a convenient way available to achieve such results. Till then, I hope the above way of sorting data by pivot column will help you get your work done.
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