Hi need help on self join and query.

I have a sales_table with sales info and below are the below columns
id
item_id
items_sold
sale_time (time stamp)

This table will have all the sales info for a given item id, and how many items sale and at what time it was sale.
Now the challenge is i need to generate a summary report of items sold for a month.
If want to get using native sql i will do below way.

select tmptable.date_month, sum(tmptable.items_sold) from
(select items_sold items_sold,
DATE_FORMAT(end_date, '%b %Y') date_month
from sales_table) tmptable
group by tmptable.date_month

Can some one help me out how to do this using hibernate criteria. As I understand we need a self join and query it.

Thanks in advance.