Question

我遇到以下问题：我想通过HQL从子级中检索父级。

Parent.hbm.xml

<hibernate-mapping>
<class name="Parent" table="Parent">
    <id name="uuid" type="java.lang.String" unsaved-value="null" access="field">
        <column name="uuid" not-null="true" />
        <generator class="org.hibernate.id.UUIDGenerator" />
    </id>

    <list name="events" table="ParentToChild" cascade="all-delete-orphan" lazy="false">
        <key column="parentUuid" />
        <index column="idx" />
        <one-to-many class="Child" />
    </list>

</class>

<query name="findParentByChild">
    <![CDATA[
         select p from Parent as p, Child as c where c.uuid = :uuid and p.uuid = c.parentUuid 
         ]]>
</query>
</hibernate-mapping>

Child.hbm.xml

<hibernate-mapping>
<class name="Child" table="Child">

    <id name="uuid" type="java.lang.String" access="field">
        <column name="uuid" not-null="true" />
        <generator class="org.hibernate.id.UUIDGenerator" />
    </id>

    <other properties..>
    </class>
 </hibernate-mapping

我可以看到为子项生成的表包含parentUuid列，所以我的问题是如何在HQL中执行此操作？我可以在HQL中使用外键吗？

Answer 1

您可以使用join：

select p Parent from Parent p join p.events c where c.uuid = :uuid

HQL从孩子那里得到父母而没有孩子知道父母

1 个答案: