There are many sites that will provide far greater detail and comment than this one. However, this is a list of basic commands that I have found repeatedly useful.

MySQL Commands

Create a database

create database databasename; 

List all databases

show databases;

Switch to a database

use databasename;

Show tables in a database

show tables;

Delete a database

drop database databasename;

Delete a table

drop table tablename;

Show data in a table

SELECT * FROM tablename;

Find a specific row from accounts with specific criteria.

SELECT * from ACCOUNTS where username = "";

Delete a row from accounts

DELETE from ACCOUNTS where username = "";

Source: http://www.pantz.org/software/mysql/mysqlcommands.html