Hi, I've a problem with a query in hibernate.

I want to select all object where a particular field is null.
If I try to make this query "from Node as n where n.parent is null" it return an empty list of object type Node.

The database table that I interrogate has this structure and the following value

NODE_ID NAME HIERARCHY_ID PARENT_NODE_ID
103 Bologna 102 104
104 Emilia Romagna 102 <null>

If I make the sql query "select * from CLASSIFICATION_NODE where PARENT_NODE_ID is null" it work correctly and return the second row.

So what or where is the problem in the hibernate query ?

Thank you.

check the generated SQL

The genereted sql:

Hibernate: select node0_.NODE_ID as NODE_ID, node0_.NAME as NAME, node0_.HIERARCHY_ID as HIERARCH3_ from HT_CLASSIFICATION_NODE node0_ where (node0_.NODE_ID is null )

..... I didn't find errors or mistakes...

The mapping file of Node class is the following:
<!DOCTYPE hibernate-mapping SYSTEM
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

<hibernate-mapping >
<class name="it.satanet.adbpo.classification.Node" table="HT_CLASSIFICATION_NODE">

<id name="id" column="NODE_ID" type="long">
<generator class="native" />
</id>


<property name="name" column="NAME" type="string" length="50" not-null="true"/>

<many-to-one name="hierarchy"
column="HIERARCHY_ID"
class="it.satanet.adbpo.classification.Hierarchy"
not-null="true"
/>

<one-to-one name="parent" class="it.satanet.adbpo.classification.Node"/>

<set name="childs"
cascade="save-update"
lazy="true">
<key column="PARENT_NODE_ID"/>
<one-to-many class="it.satanet.adbpo.classification.Node"/>
</set>

</class>
</hibernate-mapping>

Could you help me ?

Sorry, it was a mistake, I'm a new user of hibernate and I'm trying to understand how its work.

Now the query work correctly

Thank you