SQL 錯誤 (1071)：Specified key was too long; max key length is 767 bytes

Key too long issue

utf8 時，會使用 255 * 3 = 765 (bytes)
utf8mb4 255 * 4 = 1020 (so limit length is 191)

CREATE TABLE `settings` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `key` varchar(200) COLLATE utf8mb4_unicode_ci NOT NULL,
  `display_name` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
  `value` text COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `details` text COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `type` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
  `order` int(11) NOT NULL DEFAULT 1,
  `group` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `settings_key_unique` (`key`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

Replace varchar(200) with varchar(191)

Other suggestions to change mysql settings (not working! )

MySQL 問題: 1071 (42000): Specified key was too long

Reference: