Basics

show databases;
show tables;
use somedb;

Variables:

show variables like "%foo%";

Status:

show status like "%foo%";

Logging

mysql:

set GLOBAL general_log_file = '/var/log/mysql/general.log';
set GLOBAL general_log = 'ON';

Blocked Hosts

mysqladmin flush-hosts

Permissions

Current:

show grants;

Available:

show privileges;