centos6.8进入mysql之后输入查询表信息的命令没反应，输其他的命令也没反应

[root@centos6 桌面]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.1.73 Source distribution

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 tables
-> S

sql以 ; 结束，半角分号，命令行在等你输入这个符号。
另外，执行SQL前需要先选择数据库：use xxdb，这个不需要分号