Designing relationship database, a multi-paradigm

I am developing an instant message web application, and I decided to use MySQL to store my model. But I get a little confused when confronted with ORM persistence. Say I have two models, User and Message. Message has two attributes related to User, s

OneToMany Relationship in JPA 2

I've been learning JPA 2 and have learned about OneToMany and ManyToOne relationships. Here is my criteria. There are two entities, Employee and Feedback. An Employee can receive multiple feedbacks. i.e. there is ManyToOne relationship between a feed

Individual and individual forms 2.2.4

I want to write a test application for students. So there are two types of classes. Question containing a many Answer and the correct answer. So i have one-to-many and one-to-one both BIDIRECTIONAL. class Question extends Entity { static hasOne = [ a

Hibernate OneToMany bidirectional relationship is slow

I have Sessions and Users classes with following bi-directional OneToManymapping(generated with hibernate reverse engineering tool): public class Users { @OneToMany(fetch=FetchType.LAZY, mappedBy="users") public Set<Sessions> getSessionses

Hibernate / JPA ManyToOne vs. OneToMany

I am reading currently the documentation of Hibernate regarding the entity associations and I come accross a little difficulty to figure out some things. It has to do in essence with the difference between ManyToOne and OneToMany associations. Althou

Using a Multiple Owner Relationship in JDO - AppEngine

I'm new to JDO and its concept. I worked with ORMLite before which is very simple, and I can't figure out how should I do in JDO what I did in ORMLite. I have 2 entities, Broadcast and Movie. Every Broadcast has one Movie and a Movie can have many Br

Show the most common element in a SQL query

Hi All and thanks in advance for any help. This is my scenario: I have three linked tables showing production specs and type of ink used in each. Each spec can have a variable number of inks (from 1 to 10) which may or may not be the same to the othe

Rails: Add information in a multi-to-many association

I have set up a many-to-many association between users and rotas. I am trying to also store who the creator of a particular rota is. Class User has_many :rotazations has_many :rotas, :through => :rotazations Class Rota has_many :rotazations has_many

NSPrediquer to several relationships

How can I find all the categories that have subcategories with more than 1 items? I am using the following code, but I get "multiple to-many keys not allowed here". Do I need to use a SUBQUERY? NSFetchRequest *request = [NSFetchRequest fetchRequ

JPA bidirectional relationships

If I have a bidirectional Relationship in my DataModel it is the responsibility of my application to keep the references up to date in the java code. What is the best way to do this? For example a bidir. 1:N relation between A and B. @Entity class A

How to create one to several in SQLITE3?

How to create one to many in SQLITE3? I have 2 tables: Mans: _id name 1 antony 2 fred and point _id date point 1 23 77 24 99 2 25 78 5 0 I don't know SQL syntax, help me , please.Going by what iamkrillin the illin shrimp-skrillin villain: CREATE TABL

One-to-many SQL table against multiple one-to-one relationships

I'm working on a project with the following objective: A User can create a Challenge and select an optional Rival to take part of this challenge. The Challenge generates Daily entries and will track stats on these. The basic User and Entry entities l

EF code 4.1 first: one-to-many correspondence problem

In my domain I have these classes (in simplified form) public class Document { public string Id { get; set; } public IList<MetadataValue> MetadataList { get; set; } } public class MetadataValue { public string DocumentId { get; set; } public string

Hibernate WrongClassException / Sets / Discriminator?

The problem looks like this: A Product table. 3 joined-subclasses: DVD, CD, Book. A Role table (composite id: NAME, ROLE, PRODUCT), and subclasses by discriminator column ROLE: actor, director, artist, author, etc.. which are mapped to Actor, Directo