code: private ZealotKhala concat(String sqlKey, String ... params) {
          this.source.getSqlInfo().getJoin().append(SqlKeyConst.SPACE).append(sqlKey).append(SqlKeyConst.SPACE);
          if (params != null && params.length > 0) {
              for (String s: params) {
                  this.source.getSqlInfo().getJoin().append(s).append(SqlKeyConst.SPACE);
              }
          }
          return this;
      }
docs: 连接字符串.
  @param sqlKey sql关键字
  @param params 其他若干字符串参数