Hi I have a question about bag mapping.

class Parent {
private long id;//Primary key
private long dept_id ;
}

class Parent {
private long id;//Primary key
private long dept_id ;
private Parent parent;
}

the simplest forms of my classes.
I have a bag collection in parent mapping like below;

<bag name="children" table="TAB_CHILDREN" order-by="ID desc" cascade="all-delete-orphan" inverse="true" >
<key column="PARENT_ID"/>
<one-to-many class="Parent"/>
</bag>
parent.getchildren(); method generates the
select * from tab_children where parent_id= ? ; parent's id as parameter;
I want the dept_id of these tables match , i mean parent.getchildren() method generates
this sql ;
select * from tab_children where parent_id= ? and dept_id =? ; parent's id as first parameter and parent's dept_id as second parameter;

I tried to use ' where ' property of bag but i coludn't pass the dept_id of parent as parameter ;
I need this because of performance issues ,We use orcle dB and we have partitioning on dept_id columns so.

how can i get this bag definition generate second sql?