text: --  @testpoint:opengauss关键字nulls(非保留)，作为角色名
  
  
  --关键字不带引号-成功
  drop role if exists nulls;
  create role nulls with password 'gauss@123' valid until '2020-12-31';
  drop role nulls;
  
  --关键字带双引号-成功
  drop role if exists "nulls";
  create role "nulls" with password 'gauss@123' valid until '2020-12-31';
  drop role "nulls";
  
  --关键字带单引号-合理报错
  drop role if exists 'nulls';
  create role 'nulls' with password 'gauss@123' valid until '2020-12-31';
  
  --关键字带反引号-合理报错
  drop role if exists `nulls`;
  create role `nulls` with password 'gauss@123' valid until '2020-12-31';
  