[英]JPQL query: selecting a single Boolean which is the AND of two of object's fields
[英]JPQL (with Hibernate) adding fields to query, which are not desired
我有以下实体结构。
Venue -- n:1 -- Schedule -- 1:n -- Event
我有一个查询来获取场地中所有日程表的计数:
SELECT v, count(s.event) FROM Venue v
LEFT JOIN i.schedule s
GROUP BY i.id ORDER BY count(s.event) asc;
问题在于此查询将永远不会输出事件为零的场所。 问题在于Hibernate,它生成以下内容:
select ..., count(schedule4_.event_id) as col_7_0_
from Venue venue0_
left outer join event_schedule schedule4_ on venue0_.id=schedule4_.venue_id,
Event event5_
where schedule4_.event_id=event5_.id and ...
您可以看到,即使我没有要求,Hibernate也会尝试按Schedule
加入Event
。 显然,如果Schedule
不存在,则加入Event
毫无意义。
(我简化了查询,如果有错字,则对问题不会有任何影响)。
请尝试以下查询:
select v.id, count(e.id) from Venue v
left join v.schedule s
left join s.events e
group by v.id order by count(e.id) asc;
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