final public function queryPairs(
        string $query,
        string $keyField,
        string $valueField,
        string $keyPrefix = '',
        $default = false
    ): array {
        $array = $this->queryArray($query) ?: [];
        $return = [];
        foreach ($array as $row) {
            $return[$keyPrefix . ($row[$keyField] ?? '')] = $row[$valueField] ?? $default;
        }
        return $return;
    }