JPA 查询附加分组依据答案

【问题标题】：JPA query additional group byJPA 查询附加分组依据
【发布时间】：2011-12-28 04:56:01
【问题描述】：

如何为下面的 SQL 编写 JPA 查询？

select * from opstatus o where o.OPERATIONTYPE=2 and o.RECEIVEDFLAG =2 and o.SENDTIME in (select max(o1.SENDTIME)from opstatus o1 where (o1.OPERATIONTYPE=2 and o1.RECEIVEDFLAG =2) group by o1.dn);

尝试运行以下查询

result = em.createQuery("select o from DTO o where "
+ "o.operationType=:operationType"
+ " and o.receivedFlag = :receivedFlag"
+ " and o.startTime in (select max(o1.startTime)from DTO o1 where   
o1.receivedFlag = :receivedFlag group by o1.Dn) order by o.startTime").
setParameter("operationType","2").
setParameter("receivedFlag", "2").getResultList();

但是在运行时生成下面的查询，它有额外的“group by T2.DN”，我们得到“org.apache.openjpa.persistence.PersistenceException: ORA-00979: not a GROUP BY expression”

SELECT t0.OPERATIONID, t0.CURRENTSTEP, t0.DETAILEDSTEPS,t0.DN, t0.OPERATIONTYPE, t0.RECEIVEDFLAG, t0.REQUESTID, t0.SENDTIME FROM OPSTATUS t0, OPSTATUS t2 WHERE (t0.OPERATIONTYPE = ? and t0 .RECEIVEDFLAG = ? AND t0.SENDTIME IN (SELECT MAX(t1.SENDTIME) FROM OPSTATUS t1 WHERE (t1.OPERATIONTYPE = ? AND t1.RECEIVEDFLAG = ?) GROUP BY t1.DN)) GROUP BY t2.DN [params=? , ?, ?, ?]

如何防止附加“分组依据”？我尝试添加 'order by o.sendtime' 没用。

【问题讨论】：

标签： jpa openjpa

【解决方案1】：

您的意思是选择每个 Dn 组中的最后一个条目。如果两个不同的 Dn 具有相同的 startTime 并且只有一个是最后一个（最大），则您的查询将失败。因为子查询中的o1没有链接到外层的o，所以OpenJPA会生成FROM OPSTATUS t0, OPSTATUS t2

也许您可以更改您的查询。

"select o from DTO o where "
+ "o.operationType=:operationType"
+ " and o.receivedFlag = :receivedFlag"
+ " and not exists (select o1 from DTO o1 where   
o1.receivedFlag = :receivedFlag and o1.Dn = o.Dn and o1.startTime > o.startTime) order by o.startTime"

【讨论】：