After reviewing the documentation, I cannot see how to use sql-update in a realistic case.
Given:
public class Person {
private Long id; // identifier
private String name;
private String address;
private Date phone;
private Person bestfriend;
...
}
and hibernate-mapping
<class name="Person"
table="person"
<id name="id">
<generator class="native"/>
</id>
<property name="name"/>
<property name="address"/>
<property name="phone" />
<many-to-one name="bestfriend" column="bf" class="Person" />
...
</class>

What would be the signature for sql-update ? - especially if the person instance representing bestfriend can be deleted ?

When trying this in various scenarios I find that upon issuing the session.delete(aPerson), I see Hibernate trying to issue sql updates such as
update person set bf=null where bf={deleted Person id}
and when updating the person address I see:
update person set name='Jane', address='123 main st', phone='123-4567', bf=789 where id=3

From the above it seems that there are at least two different signatures for sql-update needed.

DB is mysql, Hibernate version 3.3.2