eager_loading.php

// Lazy Loading N+1 Query

$books = App\Book::all();
foreach ($books as $book) {
  echo $book->author->name;
}

// select * from books
// select * from authors where id = 1
// select * from authors where id = N


// Eager Loading 2 Query

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

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