在默认下，MySQL在use databasename的时候，是不显示连接的库名！
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| hank               |
| mysql              |
| performance_schema |
| sakila             |
| test               |
| yoon               |
+--------------------+
7 rows in set (0.00 sec)
mysql> use yoon;
Database changed
mysql>
　　可通过以下方式，实现显示连接的数据库名：
[root@hank-yoon tmp]# mysql --prompt="u(d) >"
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 29
Server version: 5.6.26-log Source distribution
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.
root((none)) >use yoon;
Database changed
root(yoon) >
　　如果想显示连接的库名和时间：
[root@hank-yoon tmp]# mysql --prompt="u(d) R:m:s >"
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 30
Server version: 5.6.26-log Source distribution
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.
root((none)) 15:20:08 >use yoon
Database changed
root(yoon) 15:20:16 >
　　也可以添加在my.cnf配置文件中，但是需要重启DB，生产库的话，可不是随便能重启，因此在连接的时候加上即可！
　　[mysql]
　　default-character-set = utf8
　　prompt = \u(\d) \R:\m:\s >