如何在Hibernate中从父表检索值到子表？

Question

我是Hibernate的新手，我在这个Employeedetails中有两个名为Employeedetails和Leaverecord的表是父，而Leaverecord是子。员工可以多次休假，我想获得特定员工的休假记录。

Mu查询是，

select a.leaverecords.leaveFrom from Employeedetails as a,Leaverecord as b where b.employeedetails.refId='1017'

但它会抛出错误， illegal attempt to dereference a collection

我的Employeedetails.hbm.xml

<hibernate-mapping>
<class name="pojo.Employeedetails" table="employeedetails" catalog="hrm">
    <id name="refId" type="java.lang.Integer">
        <column name="RefId" />
        <generator class="identity" />
    </id>
    <set name="leaverecords" table="leaverecord" inverse="true" lazy="true" fetch="select">
        <key>
            <column name="RefId" not-null="true" />
        </key>
        <one-to-many class="pojo.Leaverecord" />
    </set>
 </class>

我的Leaverecord.hbm.xml

<class name="pojo.Leaverecord" table="leaverecord" catalog="hrm">
    <id name="sno" type="java.lang.Integer">
        <column name="Sno" />
        <generator class="identity" />
    </id>
    <many-to-one name="employeedetails" class="pojo.Employeedetails" fetch="select">
        <column name="RefId" not-null="true" />
    </many-to-one>
    <property name="leaveFrom" type="date">
        <column name="LeaveFrom" length="10" not-null="true" />
    </property>
    <property name="leaveTo" type="date">
        <column name="LeaveTo" length="10" />
    </property>
    <property name="empReason" type="string">
        <column name="EmpReason" length="100" not-null="true" />
    </property>
</class>

Answer 1

试试：

   select b.`leave From` from Employeedetails as a
   inner join Leaverecord as b on a.RefId = b.RefId
   where a.refId='1017'

您有leave From列，而不是leaveFrom。