CentOS7的yum源中默认好像是没有mysql的。为了解决这个问题，我们要先下载mysql的repo源。

1. 下载mysql的repo源

$ wget http://repo.mysql.com/mysql-community-release-el7-5.noarch.rpm

2. 安装mysql-community-release-el7-5.noarch.rpm包

$ sudo rpm -ivh mysql-community-release-el7-5.noarch.rpm

安装这个包后，会获得两个mysql的yum repo源：

/etc/yum.repos.d/mysql-community.repo
/etc/yum.repos.d/mysql-community-source.repo。

3. 安装mysql

$ sudo yum install mysql-server

根据步骤安装就可以了，不过安装完成后，没有密码，需要重置密码。

注：

RPM方式安装时需要检查MySQL及相关RPM包，是否安装，如果有安装，则移除（rpm –e 名称）

 [root@localhost ~]# rpm -qa | grep -i mysql
 mysql-libs-5.1.66-2.el6_3.x86_64
 [root@localhost ~]# yum -y remove mysql-libs*

4. 重置密码

重置密码前，首先要登录

$ mysql -u root

登录时有可能报这样的错：ERROR 2002 (HY000): Can‘t connect to local MySQL server through socket ‘/var/lib/mysql/mysql.sock‘ (2)，原因是/var/lib/mysql的访问权限问题。下面的命令把/var/lib/mysql的拥有者改为当前用户：

$ sudo chown -R openscanner:openscanner /var/lib/mysql

然后，重启服务：

$ service mysqld restart

接下来登录重置密码：

$ mysql -u root
mysql > use mysql;
mysql > update user set password=password(‘123456‘) where user=‘root‘;
mysql > exit;

 PS:如果使用mysql -u root无法进入数据库或者设置密码不成功
请使用如下命令来设置root的密码

/usr/bin/mysql_secure_installation

然后直接按无密码按回车，接着根据提示设置好密码，最后一路YES

Enter current password for root (enter for none): 
OK, successfully used password, moving on...

Setting the root password ensures that nobody can log into the MySQL
root user without the proper authorisation.

Set root password? [Y/n] test123
New password: 
Re-enter new password: 
Password updated successfully!
Reloading privilege tables..
 ... Success!

若还是不成功，则需要使用mysqld_safe来启动

1）service mysqld stop
2）mysqld_safe --skip-grant-tables &
3）mysql

5. 需要更改权限才能实现远程连接MYSQL数据库

可以通过以下方式来确认：

root#mysql -h localhost -uroot -p
Enter password: ******
Welcome to the MySQL monitor.   Commands end with ; or \g.
Your MySQL connection id is 4 to server version: 4.0.20a-debug
Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the buffer.
mysql> use mysql; (此DB存放MySQL的各种配置信息)
Database changed
mysql> select host,user from user; (查看用户的权限情况)
mysql> select host, user, password from user;
+-----------+------+-------------------------------------------+
| host       | user | password                                   |
+-----------+------+-------------------------------------------+
| localhost | root | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| 127.0.0.1 | root | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| localhost |       |                                            |
+-----------+------+-------------------------------------------+
4 rows in set (0.01 sec)

由此可以看出，只能以localhost的主机方式访问。
解决方法：

mysql> Grant all privileges on *.* to 'root'@'%' identified by '123456' with grant option;

(%表示是所有的外部机器，如果指定某一台机，就将%改为相应的机器名；‘root’则是指要使用的用户名，)
mysql> flush privileges;   (运行此句才生效，或者重启MySQL)
Query OK, 0 rows affected (0.03 sec)

再次查看。。

mysql> select host, user, password from user;
+-----------+------+-------------------------------------------+
| host       | user | password                                   |
+-----------+------+-------------------------------------------+
| localhost | root | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| 127.0.0.1 | root | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
| localhost |       |                                            |
| %          | root | *4ACFE3202A5FF5CF467898FC58AAB1D615029441 |
+-----------+------+-------------------------------------------+
4 rows in set (0.01 sec)

设置开机自启动

[root@localhost ~]# chkconfig mysql on
[root@localhost ~]# chkconfig --list | grep mysql
mysql           0:off   1:off   2:on    3:on    4:on    5:on    6:off

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