HQL / JPQL - Nested select on FROM

Question

I try to convert my SQL query into HQL or JPQL (I want to benefit of the object mapping).

My SQL Request is :

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;

I try (unsuccessfully) to convert it in JPQL with :

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

But I got raised :

IllegalArgumentException occured :

org.hibernate.hql.ast.QuerySyntaxException: unexpected token: ( near line 1, column 16 [select pc from (select id, max(creationDate) from models.PushCampaign group by bde) temp, models.PushCampaign pc where pc.id = temp.id]

I read the nested select can only be in select or where clause.

Do you have workarounds to keep the request and benefit of object-mapping ?

Answer 1

Not possible with JPQL or HQL in a single request.

To do this in a single request I propose this :

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 2

this should achive similar results

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