entity-relationship

Inserting an entity and dependent entities using RIA Services

Hello everybody :-) I got a question about inserting an entity with dependent entities using RIA Services (With Silverlight 4.0). Let's say I have an Entity in my (sql) database called "Beer" and one called "Supplier", with a relationship: Beer 1 - n Supplier. There are multiple suppliers for one kind of beer. Now there's the followin...

Core data Relation Fault (not lazy loading) problem. Relations dissaper

Hello Everyone, I have a core data database which has (for now) 2 entities Product and CompetingProduct, CompetingProduct relation is set to-many with products. I create 2 mock Products and 2 mock Competing products and set relation between them .. everything works files.. Saved to database, also NSlog, "po" them.. all is good. Now.. ...

What's the point of a candidate key?

I'm fairly new to database management and this question never seems to be answered in more than one sentence. All other SO answers say "A candidate key is a minimal super key." That means nothing to me. A candidate key is supposed to specify uniqueness of a db record, correct? And a primary key is a candidate key. If a primary key alrea...

Many to many objects relations in Java Google App Engine

Maybe I misunderstood this but from what I read I may have several problems creating many to many objects relations in the data store. So I hope I am wrong. Can anyone provide me with ideas on realizing such a system on GAE/J? What I need is many students can have many files (meaning Student A can have File A and Student B can have File...

Adding "second level object" with Entity Framework (C#)

Hi everybody, I'm trying to add an object: Person (id, firstName, lastName) and another object : Details(id, personId, phoneNumber, address). Of course, the "id" column in Person and Details is auto incremented. And the "personId" foreign Key is mandatory in Details. I'm using Entity Framework. I created some basic functions ...

Saving Core Data database to sqlite file loses some recursive/circular relationship information

I have very simple circular (or self-reflecting) relationship core data model in my iPhone word game. Entity Word has one-to-many relationship to/with itself which points to related words: I use NSPersistentDocument Core Data Mac OS X template application to import words to Core Data sqlite database. After importing data I can see al...

ActiveRecord relation using an array of foreign keys

Hi, Is that possible to establish a relationship between Tree and Branch such as: class Tree < ActiveRecord::Base has_many :branches end class Branch < ActiveRecord::Base belongs_to :tree end But with an array of foreign keys branch_ids stored in Tree? I know it's the opposite of the default process, but I want to do so (just fo...

Using a db vote table for many arguments tables

Hi, I'm trying to understand if it's right to use one table for votes for more than one argument: table_votes id | vote (±1) | id_user | timestamp | argument_type | argument_id table_photos // could be argument_type = 1 id | photo_file | photo_name | etc. table_house // could be argument_type = 2 id | house_name | etc. My prob...

How to fetch one to many relationship in core data?

Hi, Let say the data entities are: Bookshop <--->> Books How do I fetch all books belonging to a specific book shop that contain "cloud" in the name for example? The following method feel clunky. Bookshop *bookshop = (Bookshop *) nsManagedObjectFromOwner; NSString *searchTerm = @"cloud"; NSFetchRequest *fetchRequest = [[NSFetchReque...

Create Dynamic LINQ BinaryExpression using data in related tables

Hello, I have an application where all queries are created dynamically based on a simple data message received by a WCF service. A data message is, put simply, a collection of columnname/column value pairs, with the addition of an operator, e.g. Equals, Less Than, etc. Simple Data Message of ColumnName-Value-Operator Name, Joe, Equal...

Cakephp Relationships

I have a few models which are not in the default cakephp format user(id, name....) 1 Harsha ... 2 John .... dishes(id, name, price ...) 1 "Cheese Pizza" 6 2 "Zinger Burger" 3 restaurants (id, name, .....) 1 "KFC" ... 2 "Pizza Hut" ... module(id, name) values (User, Dishes, Restaurants) 1 "Users" 2 "Dishes" 3 "Restaurant" i...

Relational modelling question

We have three entities called Product, ProductType, and ProductCategory. Let's pretend we have three kinds of ProductType: Book, Music, and Video. We have three different ProductCategory's for Book: Fiction, Novel, Technical. Three different ProductCategory's for Music: Rock, Jazz, Pop. And we have three different ProductCategory'...

How to save multiple entry for one entity in the same batch . Entity - Relation(One to Many) concept is use in my example.

Here is a common scenario I Have these Entity User UserId UserName ... UserQuestion UserQID UserID UserQuestion UserAnswer When the user first logon, he need to create 3 customs Answer / question. How can I Create these 3 questions relation and save it to database. I Want these questiona in relation with the specific user. ...

Rails relationship's advice.

I need to model the following relationships and would like some advice on how to properly model it. There is a user, house, apartment, garden, furniture So a user can either have a house or an apartment but not both. Both house and apartment can have furniture but only the house can have garden. So the biggest issue is user has_one ...