1、mariadb和mysql

CentOS 7 已经放弃mysql安装，而是安装mariadb。（可能是版权问题）
所以，安装centos 7安装mysql不能直接用yum install mysql命令。
需用用如下的操作进行安装。

2、下载mysql源安装包

wget http://dev.mysql.com/get/mysql57-community-release-el7-8.noarch.rpm

3.安装mysql源

yum localinstall mysql57-community-release-el7-8.noarch.rpm

4、安装mysql

yum install mysql-community-server

5、启动mysql服务

systemctl start mysqld

6.查看mysql的启动状态

systemctl status mysqld

7.设置开机启动

systemctl enable mysqld

systemctl daemon-reload

8.修改密码

需要先查看默认建立的密码：
grep 'temporary password' /var/log/mysqld.log
结果可知：
A temporary password is generated for root@localhost: HrtC<+uh>2o1

mysql登录：
mysql -u root -p
HrtC<+uh>2o1
修改密码：
mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'HrtC<+uh>2o1';
mysql> set password for 'root'@'localhost'=password('自己的密码');
注意：mysql5.7的密码策略是：大小写字母+符号
否则会报错：
ERROR 1819 (HY000): Your password does not satisfy the current policy requirements

9.查看密码策略

mysql>show variables like ‘%password%’

10.添加允许远程登录用户

grant all privileges on *.* to root@"%" identified by "自己的密码";

11.常用技巧

清屏：
方式一：Ctrl+L
方式二：\! clear