[root@yl-web yl]# yum install mysql-server
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.sina.cn
 * extras: mirrors.sina.cn
 * updates: mirrors.sina.cn
No package mysql-server available.
Error: Nothing to do

[root@yl-web yl]# mysql -u root -p
Enter password: 
Welcome to the MariaDB monitor. Commands end with ; or \g.
Your MariaDB connection id is 3
Server version: 5.5.41-MariaDB MariaDB Server

Copyright (c) 2000, 2014, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> show databases;
+--------------------+
| Database      |
+--------------------+
| information_schema |
| mysql       |
| performance_schema |
| test        |
+--------------------+
4 rows in set (0.00 sec)

MariaDB [(none)]>

[root@yl-web yl]# mysql -u root 
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.26 MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database      |
+--------------------+
| information_schema |
| mysql       |
| performance_schema |
| test        |
+--------------------+
4 rows in set (0.01 sec)

mysql>

Installed:
 mysql-community-client.x86_64 0:5.6.26-2.el7        mysql-community-devel.x86_64 0:5.6.26-2.el7        
 mysql-community-libs.x86_64 0:5.6.26-2.el7         mysql-community-server.x86_64 0:5.6.26-2.el7        

Dependency Installed:
 mysql-community-common.x86_64 0:5.6.26-2.el7                                      

Replaced:
 mariadb.x86_64 1:5.5.41-2.el7_0     mariadb-devel.x86_64 1:5.5.41-2.el7_0  mariadb-libs.x86_64 1:5.5.41-2.el7_0 
 mariadb-server.x86_64 1:5.5.41-2.el7_0