utf8mb4复杂昵称问题

wechat_ling
wl_channel_consumer  nickname
wl_consumer nickname

alter table wl_channel_consumer modify column `nickname` varchar(150) CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_unicode_ci' DEFAULT NULL COMMENT '昵称';
alter table wl_consumer modify column `nickname` varchar(255) CHARACTER SET 'utf8mb4' COLLATE 'utf8mb4_unicode_ci' DEFAULT NULL COMMENT '昵称';
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# 全局已经是mb4，没必要指定列级字符编码

mysql> show variables like '%chara%';
+--------------------------+----------------------------------+
| Variable_name            | Value                            |
+--------------------------+----------------------------------+
| character_set_client     | utf8                             |
| character_set_connection | utf8                             |
| character_set_database   | utf8                             |
| character_set_filesystem | binary                           |
| character_set_results    | utf8                             |
| character_set_server     | utf8                             |
| character_set_system     | utf8                             |
| character_sets_dir       | /usr/local/mysql/share/charsets/ |
+--------------------------+----------------------------------+
8 rows in set (0.00 sec)

+--------------------------+----------------------------------+
| Variable_name            | Value                            |
+--------------------------+----------------------------------+
| character_set_client     | utf8mb4                          |
| character_set_connection | utf8mb4                          |
| character_set_database   | utf8mb4                          |
| character_set_filesystem | binary                           |
| character_set_results    | utf8mb4                          |
| character_set_server     | utf8mb4                          |
| character_set_system     | utf8                             |
| character_sets_dir       | /usr/local/mysql/share/charsets/ |
+--------------------------+----------------------------------+

1. MySQL的版本

utf8mb4的最低mysql版本支持版本为5.5.3+，若不是，请升级到较新版本。

2. MySQL驱动

5.1.34可用,最低不能低于5.1.13

3.修改MySQL配置文件

修改mysql配置文件my.cnf（windows为my.ini）
my.cnf一般在etc/mysql/my.cnf位置。找到后请在以下三部分里添加如下内容：
[client]
default-character-set = utf8mb4
[mysql]
default-character-set = utf8mb4
[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci
init_connect='SET NAMES utf8mb4'

4. 重启数据库，检查变量
   SHOW VARIABLES WHERE Variable_name LIKE 'character_set_%' OR Variable_name LIKE 'collation%';

Variable_name Value
character_set_client utf8mb4
character_set_connection utf8mb4
character_set_database utf8mb4
character_set_filesystem binary
character_set_results utf8mb4
character_set_server utf8mb4
character_set_system utf8
collation_connection utf8mb4_unicode_ci
collation_database utf8mb4_unicode_ci
collation_server utf8mb4_unicode_ci
collation_connection 、collation_database 、collation_server是什么没关系。

但必须保证

系统变量 描述
character_set_client (客户端来源数据使用的字符集)
character_set_connection (连接层字符集)
character_set_database (当前选中数据库的默认字符集)
character_set_results (查询结果字符集)
character_set_server (默认的内部操作字符集)
这几个变量必须是utf8mb4。

5. 数据库连接的配置

数据库连接参数中:
characterEncoding=utf8会被自动识别为utf8mb4，也可以不加这个参数，会自动检测。
而autoReconnect=true是必须加上的。

6. 将数据库和已经建好的表也转换成utf8mb4

更改数据库编码：ALTER DATABASE caitu99 CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;

更改表编码：ALTER TABLE TABLE_NAME CONVERT TO CHARACTER SET utf8mb4 COLLATEutf8mb4_general_ci;
如有必要，还可以更改列的编码