many-to-many

Here's an exmaple: Originally I have 3 tables. Table B references Table A. So now Table B has two primary keys. One used as the original primary key and the other one to enforce its relationship with Tabe A. Then I want Table B to have a many-to-many relationship with Table X. As I'm adding the relationship, MySQL Workbench added Table Y with both of Table B primary keys and one primary key in Table X. So Table Y now has three primary keys. It seems like the second primary key from Table B in the junction table is unnecessary since I can identify Table B with the original primary key. So do I

I have 2 domain classes which are mapped by many-to-many relationship. I followed the instruction of Grails documentation, but I still have some problem when processing data on those domains. Here are my 2 domain classes: class User { String name int age String job static hasMany = [groups : Group] static belongsTo = [org : Organization] } class Group { String groupName String code static hasMany = [members : User] } My problems are: 1. The above relationship require one class hold belongsTo to be the "owner" of the relationship. In this context, the User belongs to the Group, but I do not

I have some entities with @ManyToMany relation: @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER) @JoinTable(name = "buses_drivers", joinColumns = @JoinColumn (name = "driver_id_inner", referencedColumnName = "driver_id"), inverseJoinColumns = @JoinColumn (name = "bus_id_inner", referencedColumnName = "bus_id")) private List<Bus> buses; and @ManyToMany(mappedBy = "buses", fetch = FetchType.EAGER, cascade = CascadeType.ALL) private List<Driver> drivers; When execute saving Driver model with some Bus models, all ok. Tables buses_drivers store all keys those entities. But when

I'll give the most basic example that I can think of for the purpose of clarity. Lets say that I have two entities of the following form: public class Student { public int Id {get;set} public string FullName {get;set;} public virtual ICollection<Course> Courses {get;set;} } public class Courses { public int Id {get;set;} public string FullName {get;set;} public virtual ICollection<Student> Students {get;set;} } Those two entities map to three tables, the third one being a table for the joins. When I query the Students like this var allStudents = context.Students; and then traverse the results

Im trying to select only specific attributes on the many-to-many relation users , just like in one-to-one. But using select() on belongsToMany() seem to be ignored and i'm still getting all the User attributes. class Computer extends Eloquent { public function users() { return $this->belongsToMany("User")->select("email"); } public function admin() { return $this->hasOne("User")->select("email"); } } Computer::with("users")->get(); Is there a way of filtering only specified columns from related entity with belongsToMany() ? Mark Yes, you actually can . Computer::with("users")->get(array(

In my project I have entities for users and companies: @Entity @Table(name = "users") public class UserDetails { @Id @GeneratedValue @Column(name = "user_id") private int id; @Column(name = "first_name") @NotEmpty @Size(min = 2, max = 20) private String firstName; @ManyToMany(cascade = CascadeType.REFRESH) @JoinTable(name = "users_companies", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "company_id")) private Set<CompanyDetails> userCompanies = new HashSet(); //getters and setters of course... } @Entity @Table(name = "companies") public class