protected function prepareDbColumns($sPrefix = '', $aCols = [])
    {
        //  Clean up
        $aCols = array_unique($aCols);
        $aCols = array_filter($aCols);

        //  Prefix all the values, if needed
        if ($sPrefix) {
            foreach ($aCols as $key => &$value) {
                $value = $sPrefix . '.' . $value;
            }
        }

        return $aCols;
    }