[root@localhost ~]# "/usr/local/mysql-8.0.11/bin/mysql" -uroot -p123456 -A

加上参数后可以看到直接就切换成功了。

[root@localhost ~]# "/usr/local/mysql-8.0.11/bin/mysql" -uroot -p123456 -A
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 41
Server version: 8.0.11 MySQL Community Server - GPL

Copyright (c) 2000, 2018, 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              |
| ncc_0807auto       |
| ncc_0807mysql      |
| performance_schema |
| sys                |
+--------------------+
6 rows in set (0.01 sec)

mysql> use ncc_0807mysql;
Database changed
mysql> 

mysql> use information_schema Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A

Database changed

当切换到某个库时，经常会出现上面信息，意思是预读这个库中表以及表列信息。

但是当库中表很多，表中数据很大时，就会出现执行use <库名>后半天没反应，连接很慢的情况

解决办法：

上面其实已经有提示了（You can turn off this feature to get a quicker startup with -A）

就是在登陆连接mysql时使用-A参数，这样就不会预读库中表信息了，能提高连接库的速度.

shell> mysql -h hostname -u username -P port -p -A

Enter password:

MySQL -A参数含义：