使用with（）仅选择laravel中DB所需的字段

Question

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

上面的循环类似于以下两个查询：

select * from books

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

如果我想使用laravel 5.6只选择下面所需的字段查询，我该怎么办？

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;
}

Answer 2

使用此：

Book::with('author:id,author_name')->get(['book_name', 'book_description', 'author_id']);