选择元素的java hql左连接查询？

Question

我在执行类似树的结构化模式的hql查询时遇到问题。以及有选择标签的元素

以下是xsd的一部分：

<xs:complexType name="School">
    <xs:sequence maxOccurs="1" minOccurs="0">
        <xs:choice>
            <xs:element name="teacher" type="tns:Teacher" />
            <xs:element name="student" type="tns:Student" />
        </xs:choice>
    </xs:sequence>
</xs:complexType>
<xs:complexType name="Teacher">
    <xs:sequence maxOccurs="unbounded" minOccurs="0">
        <xs:choice>
            <xs:element name="salaries" type="tns:Salary" />
            <xs:element name="name" type="xs:string" />
        </xs:choice>
    </xs:sequence>
</xs:complexType>
<xs:complexType name="Salary">
    <xs:attribute name="startTime" type="xs:long" />
    <xs:attribute name="endTime" type="xs:long" />
    <xs:attribute name="amount" type="xs:double" />
</xs:complexType>

以下是问题：

TypedQuery<Salary> query = em.createQuery("select sal from School  s " + 
                                                  "left join s.teacher tc "+
                                                "left join tc.salaries sal "                                                  
                                              + "where tc.name='John'", Salary.class);

我做错了什么