共计 2429 个字符，预计需要花费 7 分钟才能阅读完成。
升级原因
MySQL 默认的 utf8 只支持三字节字符，不支持 Emoji 表情符（四字节），如果有四字节的字符写入会报错。从 MySQL 5.5 开始，提供了 utf8mb4，支持四字节的字符。
许多使用 iphone 的用户来在填写昵称的时候会加入 Emoji 表情符，如果 MySQL 没有使用 utf8mb4 字符集，这样的昵称信息就无法写入。
一、升级前。
mysql> SHOW VARIABLES LIKE 'character_set%';
+--------------------------+--------------------------------------------------------------------+
| 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 | /home/sdkserver/local/mysql-5.5.43-linux2.6-x86_64/share/charsets/ |
+--------------------------+--------------------------------------------------------------------+
8 rows in set (0.00 sec)
mysql> SHOW VARIABLES LIKE 'collation%';
+----------------------+-----------------+
| Variable_name | Value |
+----------------------+-----------------+
| collation_connection | utf8_general_ci |
| collation_database | utf8_unicode_ci |
| collation_server | utf8_unicode_ci |
+----------------------+-----------------+
3 rows in set (0.00 sec)
二、修改配置文件。
打开 MySQL 的配置文件，将字符集的配置修改成如下：
[client]
default-character-set = utf8mb4
[mysql]
default-character-set = utf8mb4
[mysqld]
character-set-client-handshake = FALSE
character-set-server = utf8mb4
collation-server = utf8mb4_general_ci
init_connect='SET NAMES utf8mb4'
三、升级后。
mysql> SHOW VARIABLES LIKE 'character_set%';
+--------------------------+--------------------------------------------------------------------+
| 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 | /home/nieyong/local/mysql-5.5.43/share/charsets/ |
+--------------------------+--------------------------------------------------------------------+
8 rows in set (0.00 sec)
mysql> SHOW VARIABLES LIKE 'collation%';
+----------------------+--------------------+
| Variable_name | Value |
+----------------------+--------------------+
| collation_connection | utf8mb4_general_ci |
| collation_database | utf8mb4_general_ci |
| collation_server | utf8mb4_general_ci |
+----------------------+--------------------+
3 rows in set (0.00 sec)
本文永久更新链接地址 ：http://www.linuxidc.com/Linux/2016-07/133752.htm
正文完
星哥玩云-微信公众号
