I have this:

<hibernate-mapping>
<class name="test.A" table="A" >
<id name="a1" type="java.lang.String">
<column name="A1"/>
</id>
<many-to-one name="c" property-ref="c_id"
class="test.C" update="false" insert="false" fetch="join" >

<column name="b1" />
<column name="c1" />
</many-to-one>
</class>
</hibernate-mapping>

<hibernate-mapping>
<class name="test.C" table="C" >
<id name="c" type="java.lang.String">
<column name="C" />
</id>
<properties name="c_id" >
<property name="b1" insert="false" update="false" />
<property name="c1" insert="false" update="false" />
</properties>
</class>
</hibernate-mapping>

And i have a test whit this:

A a = (A) template.load(A.class, "1");

When in table A there is:

A1 | B1 | C1
1 null null

sql generated is:
select ... from A a0_ left outer join C c1_ on a0_.b1=c1_.b1 and a0_.c1=c1_.c1 where a0_.A1=?;

When in table A there is:

A1 | B1 | C1
1 1 1

sql generated is:
select ... from A a0_ left outer join C c1_ on a0_.b1=c1_.b1 and a0_.c1=c1_.c1 where a0_.A1=?;

BUT When I have:

A1 | B1 | C1
1 null 1

OR

A1 | B1 | C1
1 1 null

The sql is:
select ... from A a0_ left outer join C c1_ on a0_.b1=c1_.b1 and a0_.c1=c1_.c1 where a0_.A1=?
select ... from C c0_ where c0_.b1=? and c0_.c1=?

Why reason appears a query on C ?

I am using hibernate 3.2.5