[字符集] 在CentOS8.2上修改MariaDB/MySQL的預設字符集

因為MySQL是瑞典人開發的，所以預設字符集是latin1，與其每次要創建資料庫都要改，不如直接改預設字符集。

(環境：CentOS8.2, MariaDB10.3.17)

1. 先看現在的預設字符集是什麼

   [user@localhost ~]$ mysql -u user -p
   ...
   ...
   MariaDB [(none)]> \s
   --------------
   mysql  Ver 15.1 Distrib 10.3.17-MariaDB, for Linux (x86_64) using readline 5.1
   
   Connection id:          8
   Current database:
   Current user:           user@localhost
   SSL:                    Not in use
   Current pager:          stdout
   Using outfile:          ''
   Using delimiter:        ;
   Server:                 MariaDB
   Server version:         10.3.17-MariaDB MariaDB Server
   Protocol version:       10
   Connection:             Localhost via UNIX socket
   Server characterset:    latin1
   Db     characterset:    latin1
   Client characterset:    utf8
   Conn.  characterset:    utf8
   UNIX socket:            /var/lib/mysql/mysql.sock
   Uptime:                 8 sec
   

2. 為了不影響到原先就在的cnf檔，在「/etc/my.cnf.d/」資料夾下創一個「*.cnf」檔(檔名自取)，內容如下

   [client]
   default-character-set=utf8mb4        ##會修改Client與Conn.的預設字符集
   [mysqld]
   character-set-server=utf8mb4         ##會修改Server與Db的預設字符集
   collation-server=utf8mb4_unicode_ci  ##會修改預設的校驗比對方法
   

3. 重啟 MySQL，確認字符集已更改為所設定的

   [user@localhost ~]$ sudo systemctl restart mariadb
   [user@localhost ~]$ mysql -u user -p
   ...
   ...
   MariaDB [(none)]> \s
   --------------
   mysql  Ver 15.1 Distrib 10.3.17-MariaDB, for Linux (x86_64) using readline 5.1
   
   Connection id:          9
   Current database:
   Current user:           user@localhost
   SSL:                    Not in use
   Current pager:          stdout
   Using outfile:          ''
   Using delimiter:        ;
   Server:                 MariaDB
   Server version:         10.3.17-MariaDB MariaDB Server
   Protocol version:       10
   Connection:             Localhost via UNIX socket
   Server characterset:    utf8mb4
   Db     characterset:    utf8mb4
   Client characterset:    utf8mb4
   Conn.  characterset:    utf8mb4
   UNIX socket:            /var/lib/mysql/mysql.sock
   Uptime:                 3 min 39 sec