Spring Boot custom CRUD query

Question

I am using Spring Boot to create a basic chore tracker webapp. It renders as shown below, however I have hard coded in these digits so you can see what I am trying to achieve. I am trying to query the DB but cannot get it working yet. Here is the source if interested.

How can I make a custom CRUD operation to feed to my Thymeleaf html page? https://github.com/deemack/chores

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The DB has 3x tables as shown, with the completion table just having the foreign keys of the person table and chore table.

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Completion.java (model)

package org.bluegoat.chores.model;

import jakarta.persistence.*;
import lombok.Data;

@Data
@Entity
@Table(name="completion")
public class Completion {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long completion_id;

    @ManyToOne(fetch = FetchType.EAGER, optional = false)
    @JoinColumn(name="person_id", nullable = false)
    private Person person;

    @ManyToOne(fetch = FetchType.EAGER, optional = false)
    @JoinColumn(name="chore_id", nullable = false)
    private Chore chore;
}

CompletionRepository (repository)

I think I need to add a method to the CompletionRepository for the specific query

package org.bluegoat.chores.repository;

import org.bluegoat.chores.model.Completion;
import org.springframework.data.jpa.repository.JpaRepository;

public interface CompletionRepository extends JpaRepository<Completion, Long> {

//something like this that gets a list of chores of a given id, done by a person of a given id, and then count the rows in the resultset?
List<Completion> getChoreByPerson(long person_id, long chore_id); 

}

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CompletionService (service interface)

public interface CompletionService {

// And add this to the CompletionService interface?
    List<Completion> getChoreByPerson(long person_id, long chore_id);
}

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And finally Override the method in the CompletionServiceImpl CompletionServiceImpl (service)

@Service
public class CompletionServiceImpl implements CompletionService {

    private CompletionRepository completionRepository;

    public CompletionServiceImpl(CompletionRepository completionRepository) {
        super();
        this.completionRepository = completionRepository;
    }

    @Override
    public Completion getChoreByPerson(long person_id, long chore_id) {
        Optional<Completion> completion = completionRepository.getChoreByPerson(person_id, chore_id);
// Not sure what I am putting in here
    }

From the hours of videos and reading, I think I am on the right track, I just can't seem to get it to click.

There is something wrong about the person_id and chore_id being long and the Completion model fields being of type Person and Chore.