数据量很大的话，常规切换数据库会把里面所有的表遍历一遍，会很慢甚至是卡死。
解决方法：
登录的时候直接在最后面加一个 -A 就行了。
[root@localhost ~]# "/usr/local/mysql-8.0.11/bin/mysql" -uroot -p123456 -A
实战演示：
我演示的数据库就是一个数据量很大的数据库，切换数据库时半天也没有好。
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| ncc_0807auto |
| ncc_0807mysql |
| performance_schema |
| sys |
+--------------------+
6 rows in set (0.00 sec)mysql> use ncc_0807mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -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 - GPLCopyright (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>
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