MySQL
From Briki
Assigning passwords to users
Login to mysql as the relevant user and run:
SET PASSWORD = PASSWORD('biscuit');
Creating new users
Login to mysql as root, and run:
GRANT ALL ON database.* TO myuser@localhost IDENTIFIED BY 'password';
Or, to create a user with no password:
GRANT ALL ON database.* TO myuser@localhost;
Obviously, different privileges can be assigned to databases and tables. To revoke privileges, the syntax is:
REVOKE ALL ON database.* FROM myuser@localhost;