title: Updating manner of nhibernate in parent/child relationships
body: <p>I have two entities which have a parent/child relation (many to one).</p>
  
  <p>If I want to <strong>update</strong> the parent and eliminate the list of its children, it will  try to find all specified records and set their FK to Null, in order to cut the established relations between them. I totally do not have any problem with this manner because I believe that nhibernate has this ability to take care of orphaned records although there is a little problem here. </p>
  
  <p><strong>Problem :</strong> The FK Column is not Nullable so it cannot be set to Null. </p>
  
  <p>Code  </p>
  
  <pre><code>&lt;bag name="Child" inverse="false" lazy="false" access="property" cascade="All-delete-orphan" batch-size="1000"&gt;
        &lt;key&gt;
          &lt;column name="ChildCol" not-null="true"/&gt;
        &lt;/key&gt;
        &lt;one-to-many class="ChildEntityAddress"/&gt;
      &lt;/bag&gt;
  
   &lt;many-to-one name="Parent" class="ParentEntityAddress" cascade="none" fetch="join"&gt;
        &lt;column name="ParentCol" not-null="true"/&gt;
      &lt;/many-to-one&gt;
  </code></pre>
  
  <p>Is there any solution to avoid this problem ?</p>