I have following tables and corresponding classes with appropriate get/set methods for all fields.

ITEMS
ID

ORDER
ID
ITEM_ID
CUSTOMER_ID

class Item{
privater long id;
private Set orders;
...
}

class ORDER{
privater long id;
private Item item;
private long customer_id;
...
}


Could anyone suggest a HQL query that selects all items that have no orders for given customer_id?

SQL query for this looks like

SELECT ITEMS.* FROM ITEMS LEFT JOIN ORDERS ON ITEMS.ID=ORDERS.ITEM_ID AND (ORDERS.CUSTOMER_ID = ? ) WHERE (ORDERS.ITEM_ID IS NULL) ;

I'm not quite sure, i can't see all your entities,

but you can try something like that:

select item from Item as item left join item.order as order where order.customer_id = :custId and isNull(order.item)

I did not understand what else entities I need to describe
imagine there are not more entities. ;-)

provided query won't work even if it have correct syntax ;-)
like this one
select item from Item as item left join item.orders as order where order.customer_id = :custId and order.item is null;

It doesn't work because it puts criteria to where clause instead of join clause.

PS I still wounder if it _posible_ to put criteria in hibernate join clause?

Arbitary join conditions are not possible

Are there any plans to implement it in Hibernate3 or later?

Yes, its very high on the TODO list for Hibernate3, once the new parser is stable.