批量将 discuz 数据库编码从 utf8 转为 utf8mb4

为获得emoji等特殊字符支持，需要将discuz的数据库编码转换为utf8mb4。

• 确认数据库版本支持utf8mb4和utf8mb4_0900_ai_ci
• 由于用户表中username是不重复索引，且区分大小写和声调，字符集需设置为utf8mb4_general_ci
• 手动执行下面的SELECT CONCAT语句，然后使用执行结果替换该语句，保存为一个 sql 文件
• 为避免 php 运行超时，请使用 cli 工具导入保存的 sql 文件

USE `discuz_databese`;

-- 更改主库字符集

ALTER DATABASE `discuz_databese` COLLATE utf8mb4_0900_ai_ci;

-- 请使用下列语句的执行结果替换该语句

SELECT CONCAT(
  'ALTER TABLE ', `TABLE_NAME`, ' CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;'
) FROM `information_schema`.`TABLES`
  WHERE `TABLE_SCHEMA` = 'discuz_databese'
    AND `TABLE_NAME` <> 'pre_common_member'
    AND `TABLE_NAME` <> 'pre_common_member_archive'
    AND `TABLE_NAME` <> 'pre_ucenter_members';

-- 单独修改用户表（`username`字符集为`utf8mb4_general_ci`）

ALTER TABLE `pre_common_member` COLLATE utf8mb4_0900_ai_ci,
  MODIFY `email` char(40) NOT NULL DEFAULT '',
  MODIFY `username` char(15) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
  MODIFY `password` char(32) NOT NULL DEFAULT '',
  MODIFY `extgroupids` char(20) NOT NULL DEFAULT '',
  MODIFY `timeoffset` char(4) NOT NULL DEFAULT '';

ALTER TABLE `pre_common_member_archive` COLLATE utf8mb4_0900_ai_ci,
  MODIFY `email` char(40) NOT NULL DEFAULT '',
  MODIFY `username` char(15) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
  MODIFY `password` char(32) NOT NULL DEFAULT '',
  MODIFY `extgroupids` char(20) NOT NULL DEFAULT '',
  MODIFY `timeoffset` char(4) NOT NULL DEFAULT '';

ALTER TABLE `pre_ucenter_members` COLLATE utf8mb4_0900_ai_ci,
  MODIFY `username` char(15) COLLATE utf8mb4_general_ci NOT NULL DEFAULT '',
  MODIFY `password` char(32) NOT NULL DEFAULT '',
  MODIFY `email` char(32) NOT NULL DEFAULT '',
  MODIFY `myid` char(30) NOT NULL DEFAULT '',
  MODIFY `myidkey` char(16) NOT NULL DEFAULT '',
  MODIFY `regip` char(15) NOT NULL DEFAULT '',
  MODIFY `salt` char(6) NOT NULL,
  MODIFY `secques` char(8) NOT NULL DEFAULT '';

下面是写给强迫症患者的，你可能并不需要 ！！

-- 创建临时库

CREATE DATABASE `tmp123`;

-- 从原始数据库复制表（会丢弃索引）

USE `discuz_database`;

CREATE TABLE `tmp123`.`pre_common_member` AS SELECT * FROM `pre_common_member`;
CREATE TABLE `tmp123`.`pre_common_member_archive` AS SELECT * FROM `pre_common_member_archive`;

CREATE TABLE `tmp123`.`pre_ucenter_members` AS SELECT * FROM `pre_ucenter_members`;

-- 进入临时库

USE `tmp123`;

-- 转换数据库编码和字符集（已无索引，可以转换）

ALTER TABLE `pre_common_member` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
ALTER TABLE `pre_common_member_archive` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;

ALTER TABLE `pre_ucenter_members` CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci;

-- 获取重复的用户统计到临时表

CREATE TABLE `pre_ucenter_members_having_count` AS
  SELECT `username`, count(username) as `count` FROM `pre_ucenter_members`
    GROUP BY `username` HAVING `count` > 1;

-- 获取重复的用户详情到临时表

CREATE TABLE `pre_ucenter_members_having` AS
  SELECT * FROM `pre_ucenter_members` WHERE `username` IN (
      SELECT `username` FROM `pre_ucenter_members_having_count`
  );