protected function operandi($string, $set = false, $prepared = false) {
        if(empty($string) && $string !== "0") {
            return ($set ? ' = NULL' : ' IS NULL');
        }

        $firstLetter = strtolower(substr($string, 0, 1));
        switch($firstLetter) {
            case '>':
            case '<':
                $return = ' ' . $firstLetter . ' "' . intval(substr($string, 1)) . '"';
                break;
            case '.':
                $return = ' = NOW()';
                break;
            case '$':
                $rest = substr($string, 1);
                if($prepared){
                    $return = ' = UNHEX(?)';
                    $this->addExclusion($rest, 's');
                } else {
                    $return = ' = UNHEX("'.$rest.'")';
                }
                break;
            case '!':
                if(strtolower($string) == '!null' || strlen($string) == 1){
                    if($set){
                        $this->formatError(
                            [$string], 'Cannot set "NOT NULL" as value for "' . substr($string, 1) . '"'
                        );
                    }
                    $return = ' IS NOT NULL ';
                } else {
                    if($set){
                        $this->formatError([$string], 'Cannot use "!= ' . substr($string, 1) . '" to set a value');
                    }
                    $return = ' != "' . substr($string, 1) . '"';
                }
                break;
            case '{':
                $return = ' ' . substr($string, 1, -1);
                break;
            case '^':
                $return = ($set ? ' = NULL' : ' IS NULL');
                break;
            default:
                if(strtolower($string) == 'null'){
                    $return = ($set ? ' = NULL' : ' IS NULL');
                } elseif($prepared){
                    $return = ' = ? ';
                    $this->addExclusion($string);
                } else {
                    $return = ' = "' . $string . '"';
                }
                break;
        }
        return $return;
    }