How to change MySQL character_set_server & character_set_database within Ubuntu

you need find the my.cnf file location. Normally it will in /etc/ or /etc/mysql/ then you need add the fellowing code inside my.cnf

#To set the default to UTF-8, you want to add the following to my.cnf
[client]
default-character-set=utf8

[mysql]
default-character-set=utf8


[mysqld]
collation-server = utf8_unicode_ci
init-connect='SET NAMES utf8'
character-set-server = utf8

After that, you need restart Mysql and then you can check the parameter again

sudo service mysql restart
sudo mysql -u root -p
mysql> show variables like "%character%";
+--------------------------+----------------------------+
| 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 (0.01 sec)

The code above will only change the global setting of MySQL. If you want change the character_set_database of existing database. you need run the following code:

mysql> ALTER DATABASE yetiforce CHARACTER SET utf8 COLLATE utf8_general_ci;
Query OK, 1 row affected, 2 warnings (0.14 sec)
mysql> use yetiforce;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show variables like "%character%";
+--------------------------+----------------------------+
| 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 (0.01 sec)

The first line: ALTER DATABASE your-database-name CHARACTER SET utf8 COLLATE utf8_general_ci;