Mercurius系统后续的数据组织必须要用数据库啦，而且SQL作为基本的程序员技能当然要熟悉啦，跟着youtube教学视频在CentOS下安装mysql server，记录如下： 首先切换到root下安装：
yum install mysql mysql-server
检查服务状态
chkconfig mysqld --list
mysqld 0:off 1:off 2:off 3:off 4:off 5:off 6:off
启动服务
chkconfig mysqld on
启动开机服务
service mysqld start
之后给出提示信息：
PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:
/usr/bin/mysqladmin -u root password 'new-password'
/usr/bin/mysqladmin -u root -h localhost.localdomain password 'new-password'
Alternatively you can run:
/usr/bin/mysql_secure_installation
采用第二种方法更加安全。
之后需要输入root密码，注意这个root指代是mysql的root用户的密码，不是系统root用户。
然后的选项一路Y。
登录mysql，在root用户下，直接
mysql -p
登陆后，我们查看一下用户列表。
select Host,User from mysql.user;
+-----------+------+
| Host | User |
+-----------+------+
| 127.0.0.1 | root |
| localhost | root |
+-----------+------+
2 rows in set (0.00 sec)
添加一个非root用户,密码为password
CREATE USER 'lzhenn'@'127.0.0.1' IDENTIFIED BY 'password';
CREATE USER 'lzhenn'@'localhost' IDENTIFIED BY 'password';
给予新用户相应权限
GRANT ALL PRIVILEGES ON *.* TO 'lzhenn'@'localhost' WITH GRANT OPTION;
GRANT ALL PRIVILEGES ON *.* TO 'lzhenn'@'127.0.0.1' WITH GRANT OPTION;
FLUSH PRIVILEGES;
FLUSH HOSTS;
select Host,User from mysql.user;
+-----------+--------+
| Host | User |
+-----------+--------+
| 127.0.0.1 | lzhenn |
| 127.0.0.1 | root |
| localhost | lzhenn |
| localhost | root |
+-----------+--------+
4 rows in set (0.00 sec)
这里遇到一点与视频教程不太一致的地方（补充：其实密码是password，见前面identified by），新建用户的密码与root密码并不相同，查了下解决方法
update mysql.user set password=password('$NEW_PWD') where User="$YOUR_USER_NAME" and Host="localhost";
flush privileges;
Updated 2018-03-05