many-to-many

Can anyone point out a good many-to-many database tutorial for CodeIgniter. Just trying to work out the process of creating, and then updating a many-to-many relationship. My example uses a multi-select of values, wondering how you take care of monitoring changes on update etc. Donny Kurnia I'd like to share what I do in my application. This is basically same with my answer in this question . After user submit, and before entering to database, I will fetch the existing data in the database into an array. Example: $collection = array('111', '112', '113', '114'); (This is just for example. In

I'm playing aroud with Grails and am finding the ORM stuff tedious because I don't fully understand what I'm doing when it comes to domain classes. I'm hoping someone can put me back on track Consider the following Test Job One:Many Hardware Used on Job Many:One Physical Hardware ...this is analogous to the classic Order, OrderLine, Product scenario seen in university DB examples I've created the following domain classes class Job { String jobName String jobDescription } class HardwareOnJob { static hasMany = [ jobs:Job, physicalHardware:PhysicalHardware ] static belongsTo = Job String role }

I've been reading up on foreign keys and joins recently, and have been pleasantly surprised that many of the basic concepts are things I'm already putting into practice. For example, with one project I'm currently working on, I'm organizing word lists, and have a table for the sets, like so: `words` Table `word_id` `headword` `category_id` `categories` Table `category_id` `category_name` Now, generally speaking this would be a one-to-many relationship, with several words being placed under a single category with the foreign key category_id . Let's assume for a moment, however, that a user

User-Friend relationship I find an answer Entity Framework Core: many-to-many relationship with same entity and try like this. Entitys: public class User { public int UserId { get; set; } public virtual ICollection<Friend> Friends { get; set; } } public class Friend { public int MainUserId { get; set; } public User ManUser { get; set; } public int FriendUserId { get; set; } public User FriendUser { get; set; } } The fluent API: modelBuilder.Entity<Friend>() .HasKey(f => new { f.MainUserId, f.FriendUserId }); modelBuilder.Entity<Friend>() .HasOne(f => f.ManUser) .WithMany(mu => mu.Friends)

I have a many-to-many association in EF Code-First (as explained in this question), and I want to use a one-to-many to the same entity as well. The problem is EF does not produce the right database scheme. Code: public class A { public int Id { get; set; } public string Name { get; set; } public virtual ICollection<B> ObjectsOfB { get; set; } } public class B { public int Id { get; set; } public virtual A ObjectA { get; set; } public virtual ICollection<A> OtherObjectsOfA { get; set; } } When I remove the ObjectA property of class B the many-to-many association is generated correctly. When

In .NET Entity Framework, what is the best way to have a (custom) join table with extra attributes (other than ids) and/or associate this join table with others via separate model? In Ruby on Rails we can have a model for the join table, like: Item.rb (model) :has_many => :buyers, :through=>:invoice ... Buyers.rb (model) :has_many => :items, :through=>:invoice ... Invoice.rb (model) :belongs_to :item :belongs_to :buyer .... Then we can use: Item.first.buyers , Buyers.first.items and Buyer.create(:items=>Item.create(:name=>'random')) etc. just like when we use automated join table without model

I am developing with EF 4.3.1 CodeFirst. I have an Airport table as shown below: public class Airport { [Key] public int ID { get; set; } public string Name{ get; set; } } What I need is a Route table with 2 FKs from the same Airport table like: public class Route { public int DepartureAirportID { get; set; } public int DestinationAirportID { get; set; } public virtual Airport DestinationAirport { get; set; } public virtual Airport DepartureAirport { get; set; } } How can this be achieved? This should do what you need... public class Airport { public int ID { get; set; } public string Name {

Update 2009.04.24 The main point of my question is not developer confusion and what to do about it. The point is to understand when delimited values are the right solution. I've seen delimited data used in commercial product databases (Ektron lol). SQL Server even has an XML datatype, so that could be used for the same purpose as delimited fields. /end Update The application I'm designing has some many-to-many relationships. In the past, I've often used associative tables to represent these in the database. This has caused some confusion to the developers. Here's an example DB structure: