hiberante问题

   <class name="a" table="a" >
        <id name="id" column="id" type="long" unsaved-value="-1">
            <generator class="identity" />
        </id>
       <one-to-one name="b" class="b" lazy="true" cascade="all"  /></class>
<class name="b" table="b">
        <id name="userId" column="user_id" type="long">
            <generator class="foreign">
                <param name="property">a</param>
            </generator>
        </id>
        <one-to-one name="a" class="a" constrained="true" lazy="proxy" cascade="all" />
    </class>
先插入数据 然后再查询from a的时候
打印出来的语句有时是select * from a,select * from b;
打印出来的语句有时只有select * from a
希望高手帮忙解答一下！~