Supporting(ignore) descending index

[davinwang]

Mysql (8.0) supports a descending index, while sqlite not. Currently the shell script is not generate the correct DDL for sqlite. the mysql DDL

CREATE TABLE `t_sample` (
  `event_date` date,
  UNIQUE KEY `index2` (`event_date` DESC)
}

will result in

CREATE TABLE `t_sample` (
  `event_date` date,
  UNIQUE DESC
}

[dumblob]

Thanks for the bug report! Could you make a PR to fix this? I'm really out of time :cry: (and clicking merge on GitHub can be made even on my smartphone :wink:).