mysql> use dbl Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A
登錄時出現這種情況，一般是有大量庫，表，字段需要掃描，會很慢，登錄庫時可以加上-A參數不進行預讀，速度會很快。
參考http://dba.stackexchange.com/questions/62102/mysql-database-freezing-after-use/62103
On the first "use" command after login, MySQL scans database, tables and columns name for auto completion. If you have many db, tables it could take a while.
To avoid that, launch your client with the -A option (or --no-auto-rehash)
mysql>mysql -uroot -p -A</CODE>
You could also add the disable_auto_rehash variable in your my.cnf (in the [mysql] section) if you want to disable it completely. This change does not require a reboot (it is a client, not server, variable).