Medoo distinct count 統計查詢寫法

Medoo 寫法：

// 下面是meedo寫法
$data = $this->mysql->get('member_coupon_provide', [
    'count_order' => Medoo::raw('COUNT(DISTINCT(<orderNo>))'),
], [
    'sid' => $sid,
]);
return $data['count_order'];