Question

我有3个名为School，SchoolType和Country的表。您可以看到School和SchoolType之间的关系。我想要查询的是;

选择与学校类型具有相同ID的国家/地区至少有一所名为“blabla”的学校。

我的学校班级;

@JoinColumn(name = "school_type_ref", referencedColumnName = "school")
@ManyToOne(cascade = CascadeType.ALL, optional = false, fetch = FetchType.EAGER)
private SchoolType schooltype;

My SchoolType Class;

@LazyCollection(LazyCollectionOption.FALSE)
@OneToMany(cascade = CascadeType.ALL, mappedBy = "schooltype")
private List<School> schoolList;

private String id;

我的国家班级;

private String id;

Answer 1

检查一下：

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Country> c = cb.createQuery(Country.class);
Root<Country> countries = c.from(Country.class);

Subquery<Integer> sq = c.subquery(Integer.class);
Root<SchoolType> schoolTypes = sq.from(SchoolType.class);

sq.select(schoolTypes.<Integer>get("id")).where(
    cb.equal(schoolTypes.get("schoolList").get("name"), "blabla"));

c.select(countries).where(cb.in(countries.<Integer>get("id")).value(sq));

TypedQuery<Country> q = entityManager.createQuery(c);
List<Country> result = q.getResultList();

也可以尝试使用schoolTypes.<Integer>get("id")代替schoolTypes.get(SchoolType_.id)，但它永远不适合我。

我的回答是基于JPA 2.0, Criteria API, Subqueries, In Expressions

多个表上的Hibernate Criteria查询

1 个答案: