Incorrectly defined tables

Older versions of some Zen Cart plugins created tables that are no longer valid. For example:

CREATE TABLE `admin_files` (
  `id` int(11) NOT NULL,
  `page` varchar(64) NOT NULL DEFAULT '',
  `header` tinyint(4) NOT NULL DEFAULT 0,
  `submenu` tinyint(1) NOT NULL DEFAULT 0
) ENGINE=MyISAM;

ALTER TABLE `admin_files`
  ADD UNIQUE KEY `id` (`id`);

The problem with this is that it won’t work when you convert to UTF8MB4.

You will get the message:

ALTER TABLE `admin_files` DROP INDEX `id`
1075: Incorrect table definition; there can be only one auto column and it must be defined as a key

Issues like this must be fixed manually in phpMyAdmin.

ALTER TABLE admin_files ADD PRIMARY KEY (id);
ALTER TABLE admin_files DROP KEY id;