@Entity
public class Part {

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

@Entity
public class Car {

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

	@OneToMany(fetch = FetchType.LAZY)
	private List<Part> parts;
}

 create table Car (
        id bigint not null auto_increment,
        primary key (id)
    ) ENGINE=InnoDB

    create table Part (
        id bigint not null auto_increment,
        primary key (id)
    ) ENGINE=InnoDB

    create table Car_Part (
        Car_id bigint not null,
        parts_id bigint not null
    ) ENGINE=InnoDB

    alter table Car_Part 
        drop constraint UK_dlk3oyy9nxup2nhflu77chryv

    alter table Car_Part 
        add constraint UK_dlk3oyy9nxup2nhflu77chryv  unique (parts_id)
   
   alter table Car_Part 
        add constraint FK_dlk3oyy9nxup2nhflu77chryv 
        foreign key (parts_id) 
        references Part (id)

    alter table Car_Part 
        add constraint FK_r68570aqu4i9syak3l4fte2ht 
        foreign key (Car_id) 
        references Car (id)