public function build()
    {
        $params = [];
        if ($this->value !== null) {
            $op = !is_null($this->operator) ? $this->operator : '=';

            $paramName = str_replace('.', '_', $this->key);
            if ($op == 'BETWEEN') {
                $sql = "{$this->key} $op ? AND ?";

                $between = explode('AND', $this->value);

                $params[':dateFrom'] = trim($between[0]);
                $params[':dateTo'] = trim($between[1]);
            } else {
                $sql = "{$this->key} $op ?";                                    // $sql = "{$this->key} $op {$paramName}";
                $params[":{$paramName}"] = $this->value;
            }
        } else {
            $sql = $sql = "{$this->key} IS NULL ";
        }

        return [$sql, $params];
    }