How can i partition this table?

[spalat palat]

Hi,

i have a table and i need partition first for a char column and then for a date.
The first column its site_id ('AAA','BBB','CCC')

This is the table:

CREATE TABLE test
(
SITE_ID VARCHAR(3) NOT NULL,
EXPIRATION_DATE DATETIME NOT NULL,
PERIOD_DEBT_ID BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY (PERIOD_DEBT_ID,SITE_ID,EXPIRATION_DATE)
);

I cant find the way for do this, i will glad for your help!