How to use query builder for JSON data in Laravel 5.1

How can I query builder in JSON data? I'm using Guzzle. All I want is: How can I query, like searching data where amount is NOT NULL?

JSON data results:

{
  "amount": [
    {
      "member_id": "SSD",
      "sum4": null,
      "sum5": null,
      "sum6": null
    },
    {
      "member_id": "OGG",
      "sum4": 122,
      "sum5": 242,
      "sum6": 123
    },
    {
      "member_id": "PUCAN",
      "sum4": 123,
      "sum5": 443,
      "sum6": 222
    },
    {
      "member_id": "SS3TG",
      "sum4": null,
      "sum5": null,
      "sum6": null
    }
  ]
}

All I want: How can I get sum4,sum6,sum6 where not null in the JSON result?

// Pass JSON data with true as parameters to json_decode function
// It returns value as associative array
$data = json_decode($jsonData, true);

// Loop through amount
foreach($data['amount'] as $sum)
{
    // Check sum is not null
    if ($sum['sum4'] != null) {
        echo $sum['sum4'];
    // Check sum is not null
    } elseif ($sum['sum5'] != null) {
        echo $sum['sum5'];
    // Check sum is not null
    } elseif ($sum['sum6'] != null) {
        echo $sum['sum6'];
    }
}