努力使用JPA编写以下查询。
Oracle Query:
Select * from table1 s
where exists (Select 1 from table2 p
INNER JOIN table3 a ON a.table2_id = p.id
WHERE a.id = s.table3_id
AND p.name = 'Test');
另外,您是否希望指出任何优秀的教程来编写JPA中的复杂查询。
答案 0 :(得分:6)
我将使用 JpaRepository,JpaSpecificationExecutor,CriteriaQuery,CriteriaBuilder 回答简单汽车广告域(广告,品牌,型号)的示例:
<强>实体:强>
@Entity
public class Brand {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
@OneToMany(mappedBy = "brand", fetch = FetchType.EAGER)
private List<Model> models;
}
@Entity
public class Model {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
@ManyToOne
@JoinColumn(name = "brand_id")
private Brand brand;
}
@Entity
public class Advert {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@ManyToOne
@JoinColumn(name = "model_id")
private Model model;
private int year;
private int price;
}
<强>存储库:强>
public interface AdvertRepository
extends JpaRepository<Advert, Long>, JpaSpecificationExecutor<Advert> {
}
<强>规格:强>
public class AdvertSpecification implements Specification<Advert> {
private Long brandId;
public AdvertSpecification(Long brandId) {
this.brandId = brandId;
}
@Override
public Predicate toPredicate(Root<Advert> root,
CriteriaQuery<?> query,
CriteriaBuilder builder) {
Subquery<Model> subQuery = query.subquery(Model.class);
Root<Model> subRoot = subQuery.from(Model.class);
Predicate modelPredicate = builder.equal(root.get("model"), subRoot.get("id"));
Brand brand = new Brand();
brand.setId(brandId);
Predicate brandPredicate = builder.equal(subRoot.get("brand"), brand);
subQuery.select(subRoot).where(modelPredicate, brandPredicate);
return builder.exists(subQuery);
}
}
效果就是这个Hibernate SQL:
select advert0_.id as id1_0_,
advert0_.model_id as model_id5_0_,
advert0_.price as price3_0_,
advert0_.year as year4_0_
from advert advert0_
where exists (select model1_.id from model model1_
where advert0_.model_id=model1_.id
and model1_.brand_id=?)
答案 1 :(得分:1)
使用JPA Queries或HQL代替Criteria构建器可以更简单地执行此操作:
SELECT e1 from Entity1 as e1
where exists
(select e2 from Entity2 as e2 join e2.e3 as ent3
where ent3.id=e1.id and e2.name='Test')