Selecting only required fields from DB in laravel using with()

Question

foreach(Book::with('author')->get() as $book)
{ 
   echo $book->author->name;
}

Above loop is like below two queries:

select * from books

select * from authors where id in (1, 2, 3, 4, 5, ...)

If i want to select only required fields like below query using laravel 5.6, how can I do it?

select book_name, book_description from books

select author_name from authors where id in (1, 2, 3, 4, 5, ...)

Answer 1

foreach(Book::with('author' => function($query){ $query->select('id', 'author_name'); })->select('book_name', 'book_description')->get() as $book)
{ 
   echo $book->author->name;
}