Challenge 2: Write Five Query Builder Queries — Possible Solution
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use App\Models\Book;

// 1. All in-stock books, ordered by price ascending
$inStockByPrice = Book::where('in_stock', true)->orderBy('price')->get();

// 2. Books under $15
$cheapBooks = Book::where('price', '<', 15)->get();

// 3. The single book with id=3 (throws if missing)
$bookThree = Book::findOrFail(3);

// 4. All books excluding out-of-stock ones
$availableBooks = Book::where('in_stock', '!=', false)->get();
// equivalently: Book::whereNot('in_stock', false)->get();

// 5. The count of all books
$totalBooks = Book::count();

WHY THIS WORKS
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- Book::where('in_stock', true)->orderBy('price')->get() chains three
  method calls, but Eloquent (like Django's QuerySet) only actually runs
  the SQL once the query is built and terminated with something like
  ->get() — the same lazy-until-evaluated principle Django's Course 1
  covered for QuerySets applies to Eloquent's query builder too.
- Book::where('price', '<', 15) uses the three-argument form of where():
  column, operator, value — Eloquent supports comparison operators
  directly as the second argument, rather than Django's __lt-style
  double-underscore suffix on the field name.
- Book::findOrFail(3) is appropriate here specifically because a primary
  key lookup is guaranteed to match at most one row — mirroring exactly
  when Django's course recommended .get() as safe: a primary-key-based
  fetch, not an arbitrary field filter that could plausibly match zero or
  several rows.
- Book::count() runs a SQL COUNT(*) query directly, rather than fetching
  every row into a PHP collection and counting them in memory — the same
  performance reasoning Django's .count() QuerySet method follows.