Hi,


Sorry, I've been struggling to clarify the terms. In my case below, I've 3 classes: LegalPerson, Address and Contact.

As a trial, I managed to get it done (i.e. have data records updated as expected) for the many-to-one relationship on LegalPerson-Address.

I was trying ONE-TO-ONE relationship for LegalPerson-Contact. (In the LegalPerson class,"contacts" is one of the properties) Schema generated the respective tables. However, the LegalPerson table DOES NOT have the expected field "contacts", which I would expect to update as the id for Contact class. How should I deal with ONE-TO-ONE relationship? Is it NECESSARY for me to add a "legalPerson" property inside Contact class to reference back to have the updat work?

thanks in advance. My LegalPerson.hbm.xml below:


<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
<class name="RHU.RAIS.Business.LegalPerson, RHU.RAIS.Business" table="LegalPerson">
<id name="id">
<column name="id" not-null="true"/>
<generator class="native" />
</id>
<!-- A LegalPerson has to have a name, but it shouldn' be too long. -->
<property name="name">
<column name="name" length="255" not-null="true" />
</property>
<property name="legalPersonType">
<column name="legalPersonType" length="1"/>
</property>
<property name="legalId">
<column name="legalId" length="15"/>
</property>
<many-to-one name="addresses" class="RHU.RAIS.Business.Address, RHU.RAIS.Business" cascade="all" outer-join="true" column="addresses"></many-to-one>
<one-to-one name="contacts" class="RHU.RAIS.Business.Contact, RHU.RAIS.Business" cascade="all" outer-join="true"></one-to-one>
</class>
</hibernate-mapping>

If you have a field in the LegalPerson table for the contact, then it's not a one-to-one relationship, but a many-to-one. The database terminology is used here.

Excuse if I misunderstood:

Let set a Person has one Contact record only. Shouldn't it be one-to-one? Expect a reference field at the Person table to point to Contact record.

I interpreted that a many-to-one case would mean many Persons pointing to a single Contact record.

Sorry, need clarifications here.

As I said, it's standard terminology so if you Google for database relationship types, you should find plenty of explanations. For example, this one: http://www.onlamp.com/pub/a/onlamp/2001/03/20/aboutSQL.html.

In short, if there's a reference field in Person table to point to Contact record, nothing prevents many persons pointing to a single Contact record and that's why it's called many-to-one.