How to get the Max of Total in JPA? - jpa

Question

Hi I have to write JPQL command that does something specific the question is exactly:
"Find those students that has the greatest total of studypoint scores?"
There are just two Entity classes that looks like :
#Entity
#Table(name = "student")
#XmlRootElement
#NamedQueries({
#NamedQuery(name = "Student.findAll", query = "SELECT s FROM Student s"),
#NamedQuery(name = "Student.findById", query = "SELECT s FROM Student s WHERE s.id = :id"),
#NamedQuery(name = "Student.findByFirstname", query = "SELECT s FROM Student s WHERE s.firstname = :firstname"),
#NamedQuery(name = "Student.findByLastname", query = "SELECT s FROM Student s WHERE s.lastname = :lastname")})
public class Student implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "ID")
private Integer id;
#Column(name = "FIRSTNAME")
private String firstname;
#Column(name = "LASTNAME")
private String lastname;
#OneToMany(mappedBy = "studentId", cascade = CascadeType.PERSIST)
private List<Studypoint> studypointCollection;
public void addStudyPoint(Studypoint cc) {
if (studypointCollection == null) {
studypointCollection = new ArrayList<>();
}
studypointCollection.add(cc);
cc.setStudentId(this);
}
and the other class
#Entity
#Table(name = "studypoint")
#XmlRootElement
#NamedQueries({
#NamedQuery(name = "Studypoint.findAll", query = "SELECT s FROM Studypoint s"),
#NamedQuery(name = "Studypoint.findById", query = "SELECT s FROM Studypoint s WHERE s.id = :id"),
#NamedQuery(name = "Studypoint.findByDescription", query = "SELECT s FROM Studypoint s WHERE s.description = :description"),
#NamedQuery(name = "Studypoint.findByMaxval", query = "SELECT s FROM Studypoint s WHERE s.maxval = :maxval"),
#NamedQuery(name = "Studypoint.findByScore", query = "SELECT s FROM Studypoint s WHERE s.score = :score")})
public class Studypoint implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Basic(optional = false)
#Column(name = "ID")
private Integer id;
#Column(name = "DESCRIPTION")
private String description;
#Column(name = "MAXVAL")
private Integer maxval;
#Column(name = "SCORE")
private Integer score;
#JoinColumn(name = "STUDENT_ID", referencedColumnName = "ID")
#ManyToOne
private Student studentId;
As you can see Student can have many Studypoints. Which I really struggle is this JPQl: Please help.

Answer 1

I tried for sometime to get this working with JQL and I can't see how you wrap the max in the sum, so I switched to SQL.
It's not ideal, but here is my repository:
package net.isban.fmis.repository;
import net.isban.fmis.entity.Studypoint;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
#Repository
public interface StudyPointRepository extends CrudRepository<Studypoint, Integer> {
#Query(value="select top 1 id from (select sum(score) scoresum, student.id from studypoint join student on student.id=studypoint.student_id group by student.id) order by scoresum desc", nativeQuery=true)
Integer findStudentIdWithMaxScore();
}