带有内部 SELECT 语句的 JPA Criteria Builder 查询

Question

我需要使用 JPA 条件生成器创建以下 SQL 连接条件，

SELECT * FROM student s1
INNER JOIN
(SELECT subject,teacher,MIN(marks) AS marks FROM student GROUP BY subject, teacher) s2
ON s1.subject = s2.subject
AND s1.teacher = s2.teacher
AND s1.marks = s2.marks

下面是实体 class 和 JPA 查询生成器。

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
public class Student implements Serializable {
    
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="id")
    Long id;
    
    @Column(name="name")
    String name;
    
    @Column(name="subject")
    public
    String subject;
    
    @Column(name="teacher")
    String teacher;
    
    @Column(name="marks")
    String marks;
    
    @JsonIgnore
    @ManyToOne
    @JoinColumns({
    @JoinColumn(insertable=false, updatable=false, name="subject",referencedColumnName="subject"),
    @JoinColumn(insertable=false, updatable=false, name="teacher",referencedColumnName="teacher"),
    @JoinColumn(insertable=false, updatable=false, name="marks",referencedColumnName="marks")
    })
    Student studentSelf;
    
    @JsonIgnore
    @OneToMany(cascade = CascadeType.ALL, mappedBy="studentSelf")
    Set<Student> studentref;

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<Student> query = cb.createQuery(Student.class);
Root<Student> mainStudent = query.from(Student.class);
List<Predicate> predicates = new ArrayList<>();

Join<Student, Student> studentJoin = mainStudent.join("studentSelf", JoinType.INNER);
        
List<Student> list = entityManager.createQuery(query).getResultList();

我可以使用连接条件构建查询，但无法创建内部 SELECT 查询。我如何为连接子句创建内部 select 查询？

需求说明: 下面是需要的输入table和输出

Answer 1

我还没有尝试过这个，它云失败了，但有一个例外。但是你能试一试吗？

删除 studentSelf 和 studentRef 如果您只是为此查询添加了它们。 @ManyToOneonstudentSelf` 也不是，因为它会指向许多记录
我认为以下查询等同于您要实现的目标。

    SELECT * 
    FROM student s1
    WHERE s1.marks 
    IN
    (
      SELECT MIN(s2.marks) 
      FROM student s2
      where s1.subject = s2.subject
      AND  s1.teacher = s2.teacher
    )

然后我试着把它翻译成CriteriaQuery

    CriteriaBuilder cb = em.getCriteriaBuilder();
    CriteriaQuery<Student> query = cb.createQuery(Student.class);
    Root<Student> mainStudent = query.from(Student.class);

    Subquery<Student> subQuery = query.subquery(Student.class);
    Root<Student> subQueryRoot = subQuery.from(Student.class);

    Predicate predicate1 = cb.equal(mainStudent.get("teacher"), 
                                    subQueryRoot.get("teacher"));
    Predicate predicate2 = cb.equal(mainStudent.get("subject"), 
                                    subQueryRoot.get("subject"));
    Predicate finalPredicate = cb.and(predicate1, predicate2);

    subQuery.select(cb.min(subQueryRoot.get("marks"))).where(finalPredicate);

    query.select(mainStudent).where(mainStudent.get("marks").in(subQuery));
    em.createQuery(issueQuery).getResultList();

更新

已根据 vinay-s-g 条评论

将 subquery.correlate(mainStudent); 更新为 subQuery.from(Student.class);

Answer 2

对上述答案进行了细微修改，

        CriteriaBuilder cb = entityManager.getCriteriaBuilder();
        CriteriaQuery<Student> query = cb.createQuery(Student.class);
        Root<Student> mainStudent = query.from(Student.class);

        Subquery<Student> subQuery = query.subquery(Student.class);
        Root subQueryRoot = subQuery.from(Student.class);

        Predicate predicate1 = cb.equal(mainStudent.get("teacher"), 
                                        subQueryRoot.get("teacher"));
        Predicate predicate2 = cb.equal(mainStudent.get("subject"), 
                                        subQueryRoot.get("subject"));
        Predicate finalPredicate = cb.and(predicate1, predicate2);

        subQuery.select(cb.min(subQueryRoot.get("marks"))).where(finalPredicate);

        query.select(mainStudent).where(mainStudent.get("marks").in(subQuery));
        return entityManager.createQuery(query).getResultList();

带有内部 SELECT 语句的 JPA Criteria Builder 查询

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