private void createTablesIfNotExist(Connection cnn) {
        if (tableExists("cb_users", cnn)) {
            logger.info("table cb_users already exists");
        } else {
            logger.info("create table cb_users");
            String sql =
                    "CREATE TABLE `cb_users` (                 \n" +
                            "  `username` varchar(255) NOT NULL,       \n" +
                            "  `password` varchar(255) DEFAULT NULL,   \n" +
                            "  PRIMARY KEY (`username`)                \n" +
                            ")                                         \n";
            executeStatement(sql, cnn);
        }


        if (tableExists("cb_groups", cnn)) {
            logger.info("table cb_groups already exists");
        } else {
            logger.info("create table cb_groups");
            String sql =
                    "CREATE TABLE `cb_groups` (                        \n" +
                            "  `groupname` varchar(255) NOT NULL,      \n" +
                            "  `username` varchar(255) NOT NULL,       \n" +
                            "  `ID` int(11) NOT NULL AUTO_INCREMENT,   \n" +
                            "  PRIMARY KEY (`ID`),                     \n" +
                            "  UNIQUE KEY `ID_UNIQUE` (`ID`)           \n" +
                            ")                                         \n";
            executeStatement(sql, cnn);

        }
    }