你可以这样做，如果它不工作，你需要重新启动mysql。

《NijaCat》也很接近，但却过于夸张:

要将默认值设置为UTF-8，您需要将以下内容添加到my.cnf

[client]
default-character-set=utf8

[mysqld]
default-character-set = utf8

然后，验证:

mysql> show variables like "%character%";show variables like "%collation%";

+--------------------------+----------------------------+
| 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/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

+----------------------+-----------------+
| Variable_name        | Value           |
+----------------------+-----------------+
| collation_connection | utf8_general_ci |
| collation_database   | utf8_general_ci |
| collation_server     | utf8_general_ci |
+----------------------+-----------------+
3 rows in set (0.00 sec)

如果你在使用MySQL Workbench确认客户端的字符集支持时遇到麻烦，那么请记住以下注意事项:

重要的 MySQL Workbench打开的所有连接都会自动设置客户端字符 设置为utf8。手动更改客户端字符集，例如使用set NAMES .．.，可能导致MySQL Workbench不能正确显示字符。为 有关客户端字符集的其他信息，请参见连接字符集 和排序。

因此，我无法用my.cnf更改覆盖MySQL Workbench的字符集。如。设置名称utf8mb4

MySQL 5.5，所有你需要的是:

[mysqld]
character_set_client=utf8
character_set_server=utf8
collation_server=utf8_unicode_ci

Collation_server是可选的。

mysql> show variables like 'char%';
+--------------------------+----------------------------+
| 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/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

MySQL v5.5.3及更高版本:

只在[mysqld]部分中添加三行:

[mysqld]
character-set-server = utf8
collation-server = utf8_unicode_ci
skip-character-set-client-handshake

注意:在这里包含skip-character-set-client-handshake可以避免在[mysqld]中包含init-connect，在[client]和[mysql]部分中包含default-character-set。

对于utf8mb4_general_ci

[client]
default-character-set=utf8mb4

[mysql]
default-character-set=utf8mb4
    
[mysqld]
collation-server = utf8mb4_general_ci
init-connect='SET NAMES utf8mb4'
character-set-server = utf8mb4

根据symfony框架文档https://symfony.com/doc/2.6/book/doctrine.html#configuring-the-database

我们建议不要使用MySQL的utf8字符集，因为它没有 支持4字节unicode字符，包含它们的字符串将是 截断。更新的utf8mb4字符集修复了这个问题。