Laravel从2张桌子中选择

I've searched a lot and can't find a solution. I have 3 tables, one shopping_carts table, one product and finally an items table. I have created an eshop and I want to display the quantity of each product after a user clicks the add to cart button. My code is below but that returns only the product that exists in items table and it's logic. I need the quantity of that product in items table but I need also the rest products from the products table.

 return $query = Product::select('title','price','imageUrl','quantity','products.id')
           ->join('items','items.product_id','=','products.id')
           ->where('shopping_cart_id', '=' ,$id)->get();

shopping_carts

products

items

You can achieve this in two ways:-

First one is by using relationships from here https://laravel.com/docs/5.7/eloquent-relationships

The second one is by modifying your existing query:-

return $query = Product::select('title','price','imageUrl','quantity','products.id')
       ->leftJoin('items','items.product_id','=','products.id')
       ->where('shopping_cart_id', '=' ,$id)->get();

Try this

$products = DB::table('items')
    ->join('products', 'items.product_id', '=', 'products.id')
    ->where('shopping_cart_id', '=' , $id)
    ->get();

Or Using relationships

class ShoppingCart extends Model
{
    public function items()
    {
        return $this->hasMany('App\Item');
    }
}

class Item extends Model
{
    public function product()
    {
         return $this->belongsTo('App\Product');
    }
}

then use

$shopping_cart = ShoppingCart::with(['items', 'items.product'])->find($id);

Updated answer with all product

Product::select('products.id', 'products.title', 'products.price', 'products.imageUrl', 
                 DB:raw('(CASE WHEN items.qunatity IS NULL THEN 0 ELSE items.qunatity END) as quantity')
       ->leftJoin('items', function($join) use($id){
            $join->on('products.id', '=', 'items.product_id')
                ->on('items.shopping_cart_id', '=', $id);
        })->get();

i found the answer with some changes to noufalcep code

return Product::select('products.id', 'products.title', 'products.price', 'products.imageUrl',
           DB::raw('CASE WHEN items.quantity IS NULL THEN 0 ELSE items.quantity END as quantity'))
       ->leftJoin('items', function($join) use($id){
           $join->on('products.id', '=', 'items.product_id')
               ->where('items.shopping_cart_id', '=', $id);
       })->get();