How to Retrieve Nested Relationships in Laravel: Accessing Persons Subscribed to an Event Across Multiple Intermediary Tables?

Nested Relationships in Laravel

Nested relationships allow you to access models that are several levels deep in your data structure. This can be a challenge to achieve in Laravel, especially with complex relationships.

Problem Statement:

Retrieving a list of persons subscribed to an event, despite multiple intermediary tables between the event and person models.

Database Structure:

The database structure involves the following tables: events, cities, companies, and persons.

Model Relationships:

• Event: Belongs to City
• City: Has many Companies, Has many Events
• Company: Belongs to City, Has many Persons
• Person: Belongs to Company, Belongs to Many Events (through EventScore)

Unsuccessful Attempts:

Attempts to use with() and whereHas() methods did not produce the desired result.

Solution:

To solve this problem, use the following query:

return Event::with('city.companies.persons')->get();

This query eager loads the city, companies, and persons associated with the event.

Alternatively, if you wish to select only specific fields from the persons table:

return Event::with(['city.companies.persons' => function ($query) {
    $query->select('id', '...');
}])->get();

This approach ensures that only the specified fields are retrieved, optimizing the query.

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