[英]How to I query sql for a Object in a Table with a single sub-object based on a field?
我现在所拥有的是:
获取所有社区等的List<Town>
:
(Town) em.createQuery(from Town towns"
+ " left join fetch towns.neighborhoods neighborhood"
+ " left join fetch neighborhood.population population"
+ " left join fetch population.age age"
+ " where age.value = :ageValue")
.setParameter("ageValue", ageValue)
我想得到一个只有一个邻居的List<Town>
,这是第一个在neighborhood.creationDate
。
我怎么做 ?
我不想全部拿走然后将其删除。
谢谢。
我建议在where子句中添加一个子查询,如下所示:
where age.value = :ageValue
AND neighborhood.creationDate =
(Select max(nh.creationDate) From Neighborhood nh
where nh.townsId = towns.townsId)
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