How Can I Selectively Retrieve Columns from Joined Tables Using Laravel Eloquent's `with()` Function?

Selective Column Retrieval with "With()" Function in Laravel Eloquent

A common requirement when working with Eloquent models is the need to join multiple tables and retrieve specific columns from the joined tables. While the "with()" function provides a convenient way to specify relationships, it initially fetches all columns from related tables.

In the example provided, the goal is to retrieve specific columns (id and username) from the "users" table while using "with()" to join it with the "posts" table. The initial implementation fetches all columns from both tables, resulting in the following queries:

select * from `posts`
select * from `users` where `users`.`id` in (<1>, <2>)

To retrieve only the desired columns from the joined table, a closure function can be passed as the second parameter to "with()" as follows:

Post::query()
    ->with(['user' => function ($query) {
        $query->select('id', 'username');
    }])
    ->get()

This modification will execute the following queries:

select * from `posts`
select id, username from `users` where `users`.`id` in (<1>, <2>)

This approach ensures that only the specified columns are retrieved from the joined table while utilizing the "with()" function for relationship joining.

Important Note:

It's crucial to include the primary key (id in this case) as the first parameter in the $query->select() within the closure function. This is necessary to correctly retrieve the results from the joined table.

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