Question

我在本机查询中遇到了一件奇怪的事情：

如果我尝试使用命名本机查询，如下所示

@NamedNativeQuery(name = "native_count_avg_guest_quizzes", resultClass = java.math.BigDecimal.class, query = "select avg(c) as r from ((select count(*) as c from user_quiz uq join user u on (uq.user_id = u.id) where u.status = 'temporary' group by u.id) as res)")

应用程序无法运行，我有

org.hibernate.HibernateException: Errors in named queries: native_count_avg_guest_quizzes_

但是如果我不使用NamedNativeQuery并且仅创建如下的动态本机查询，则相同的查询工作正常：

entityManager.createNativeQuery(
                        "select avg(c) as r from ((select count(*) as c from user_quiz uq join user u on (uq.user_id = u.id) where u.status = 'temporary' group by u.id) as res)")
                        .getSingleResult()

为什么呢？我在使用NamedNativeQuery做错了什么？感谢

更新实体类如下

@Entity
@Table(name = "user_quiz")
@NamedNativeQueries({
    @NamedNativeQuery(name = "native_count_avg_guest_quizzes", resultClass = java.math.BigDecimal.class, query = "select avg(c) as r from ((select count(*) as c from user_quiz uq join user u on (uq.user_id = u.id) where u.status = 'temporary' group by u.id) as res)")
})
@NamedQueries({
    @NamedQuery(name = "list_clients_quizzes", query = "select uq from UserQuiz uq where uq.quiz.client.id = :clientId"),
    .......
})
public class UserQuiz extends Measurable {
.......
}

Answer 1

createNativeQuery用于本地SQL查询语言，这意味着DB可以理解并执行该查询（例如，select * from some_table where id = '0001'）;

可能会导致数据库依赖。现在您使用JPQL语言，这就是为什么，使用createQuery()或createNameQuery()与@NameQuery注释一起唱歌。

示例：

<强> @NameQuery

@NamedQuery(name = "findAllEmployee", query = "select e from Employee e")
@Entity
public class Employee {
    @Id int id;
    String name;
    // ...
}

Query query = em.createNamedQuery("findAllEmployee");
query.getResultList()

动态

    Query query = em.createQuery("select e from Employee e");
    query.getResultList()?

* <强>本地

Query query = em.createNativeQuery("SELECT * FROM EMPLOYEE_TBL");
query.getResultList()?

Answer 2

从@NamedNativeQuery中删除resultClass。

请参阅https://stackoverflow.com/a/9763489

对于NamedNativeQueries，只有在结果实际映射到实体时才能使用resultClass。

jpa和本机查询

2 个答案: