mysql 错误解决大法 Specified key was too long; max key length is 767 bytes

高版本mysql向低版本（5.7以下）导入sql时可能会发生此问题

开启索引最大长度

SET GLOBAL INNODB_LARGE_PREFIX = ON;

将表改为动态表
SET GLOBAL innodb_file_format = BARRACUDA;

设值表的行记录格式为Dynamic

    创建表时CREATE TABLE `users` (
    `username` varchar(50) NOT NULL,
  `password` varchar(500) NOT NULL,
   `enabled` tinyint(1) NOT NULL,
  PRIMARY KEY (`username`) USING BTREE
  ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 ROW_FORMAT=DYNAMIC;