Relate two more tables

To achieve this using Eloquent, you can utilize relationships to join multiple tables and retrieve the desired column from the CityPopulation model. Here's a step-by-step guide on how you can set this up:

1. Define Relationships in Your Models:

   • Author Model: Define a relationship to the AuthorCity model.
   • AuthorCity Model: Define a relationship to the CityPopulation model.

2. Use Eager Loading in the Posts Model:

   • Use Eloquent's eager loading to fetch the related data.

Here's how you can set up these relationships:

Step 1: Define Relationships

Author Model:

class Author extends Model
{
    public function authorCity()
    {
        return $this->hasOne(AuthorCity::class);
    }
}

AuthorCity Model:

class AuthorCity extends Model
{
    public function cityPopulation()
    {
        return $this->belongsTo(CityPopulation::class);
    }
}

Step 2: Eager Load in the Posts Model

In your Posts model or wherever you are querying the Posts, you can use eager loading to bring in the numberPopulation from the CityPopulation model:

$posts = Post::with(['author.authorCity.cityPopulation'])->get();

foreach ($posts as $post) {
    $numberPopulation = $post->author->authorCity->cityPopulation->numberPopulation ?? 'N/A';
    echo "Post ID: {$post->id}, Population: {$numberPopulation}\n";
}

Explanation:

• with(['author.authorCity.cityPopulation']): This line tells Eloquent to load the author relationship on the Post model, then the authorCity relationship on the Author model, and finally the cityPopulation relationship on the AuthorCity model.
• numberPopulation: Access the numberPopulation column from the CityPopulation model.

This setup assumes that your database relationships are correctly defined with foreign keys. Adjust the relationship methods if your table and column names differ.