laravel - Getting just the latest value on a joined table with Eloquent

Question

I have two tables like this:

products:

+----+-----------+
| id |   name    |
+----+-----------+
|  1 | Product 1 |
|  2 | Product 2 |
|  3 | Product 3 |
|  4 | Product 4 |
+----+-----------+

prices:

+----+-------+------------+---------------------+
| id | price | product_id |     created_at      |
+----+-------+------------+---------------------+
|  1 |    20 |          1 | 2014-06-21 16:00:00 |
|  2 |    10 |          1 | 2014-06-21 17:00:00 |
|  3 |    50 |          2 | 2014-06-21 18:00:00 |
|  4 |    40 |          2 | 2014-06-21 19:00:00 |
+----+-------+------------+---------------------+

I have this relationship on Product:

public function prices()
{
    return $this->hasMany('Price');
}

I can easily run Product::with('prices')->get(); to get each product with each of the prices it's had.

How can I use Eloquent to only get the most recent price? (Also, what if I wanted the cheapest/most expensive price instead?)

Answer 1

You can tweak your relations to get what you want. Accepted answer of course works, however it might be memory overkill with lots of data.

Find out more here and there.

Here's how to use Eloquent for this:

// Product model
public function latestPrice()
{
   return $this->hasOne('Price')->latest();
}

// now we're fetching only single row, thus create single object, per product:
$products = Product::with('latestPrice')->get();
$products->first()->latestPrice; // Price model

That's nice, but there's more. Imagine you'd like to load highest price (just a value) for all the products:

public function highestPrice()
{
   return $this->hasOne('Price')
      ->selectRaw('product_id, max(price) as aggregate')
      ->groupBy('product_id');
}

Not very convenient yet:

$products = Product::with('highestPrice')->get();
$products->first()->highestPrice; // Price model, but only with 2 properties
$products->first()->highestPrice->aggregate; // highest price we need

So add this accessor to make the life easier:

public function getHighestPriceAttribute()
{
    if ( ! array_key_exists('highestPrice', $this->relations)) $this->load('highestPrice');

    $related = $this->getRelation('highestPrice');

    return ($related) ? $related->aggregate : null;
}

// now it's getting pretty simple
$products->first()->highestPrice; // highest price value we need