Question

我尝试将我的SQL查询转换为HQL或JPQL（我想从对象映射中受益）。

我的SQL请求是：

SELECT * 
FROM (SELECT bde, MAX(creation_date) 
      FROM push_campaign GROUP BY bde) temp, 
push_campaign pc where pc.bde = temp.bde and pc.creation_date = temp.creation_date;

我尝试（不成功）在JPQL中将其转换为：

select pc 
from (select bde, max(creationDate) 
      from PushCampaign group by bde) temp, 
PushCampaign pc 
where pc.bde = temp.bde and pc.creationDate = temp.creationDate

但我得到了成长：

IllegalArgumentException occured :
org.hibernate.hql.ast.QuerySyntaxException：意外令牌:(近第1行，第16列[从中选择pc（选择id，max（creationDate）） models.PushCampaign group by bde）temp，models.PushCampaign pc where pc.id = temp.id]

我读过嵌套的select只能在select或where子句中。

您是否有解决方法来保持对象映射的请求和好处？

Answer 1

这应该得到类似的结果

select pc
from PushCampaign pc 
where pc.creationDate =
(select max(creationDate) from PushCampaign inner where inner.bde = pc.bde)

Answer 2

单个请求中无法使用JPQL或HQL。

要在一个请求中执行此操作，我建议：

String campaignToLaunch = "select pc.* from PushCampaign pc ..."
//SQL request which return a resultset compatible with the models.PushCampaign class
Class className = Class.forName("models.PushCampaign");
List<PushCampaign> result = JPA.em()
                           .createNativeQuery(campaignToLaunch,className)
                           .getResultList();

Answer 3

一个简单的解决方案可能是：

servlet
{
    Query q = entityManager.createNativeQuery("SQL");
    List<> li =  q.getResultList();

    @PersistenceContext(unitName="UNIT")
    private EntityManager entityManager;
}

HQL / JPQL - 在FROM上嵌套选择

3 个答案: