one-to-many

Hibernate 1:M relationship ,row order, constant values table and concurrency

table A and B need to have 1:M relationship a and b are added during application runtime, so A created, then say 4 B's created. Each B instance has to come in order, so that I could later extract them in the same order as I added them. The app will be a web-app running on Tomcat, so 10 instances may work simultaneously. So my question...

Get the ID of a Child in a cascade="all" relationship, while adding it to a collection, in Hibernate

Hi, i have two Entities, "Parent" and "Child", that are linked through a bidirectional one-to-many relationship with the cascade attribute set to "all". When adding a Child object to the Parent children collection using the code below, i can't get the ID of the persisted child until i commit the transaction: Parent p = (Parent) session....

Nhibernate one-to-many with table per subclass

I am customizing N2CMS's database structure, and met with an issue. The two classes are listed below. public class Customer : ContentItem { public IList<License> Licenses { get; set; } } public class License : ContentItem { public Customer Customer { get; set; } } The nhibernate mapping are as follows. <class name="N2.ContentI...

@OneToMany and composite primary keys?

Hi, I'm using Hibernate with annotations (in spring), and I have an object which has an ordered, many-to-one relationship which a child object which has a composite primary key, one component of which is a foreign key back to the id of the parent object. The structure looks something like this: +=============+ +=======...

Delete element from Set

Hi. I have 2 classes Tema(Homework) and Disciplina (course), where a Course has a Set of homeworks. In Hibernate i have mapped this to a one-to-many associations like this: <class name="model.Disciplina" table="devgar_scoala.discipline" > <id name="id" > <generator class="increment"/> </id> <set name="listaTeme" table="devgar_sc...

Hibernate: What's wrong with this mapping to a subclass joined on foreign key?

I am experimenting with Hibernate to gain experience. I created a class Person with two subclasses: Student and Worker: public abstract class Person { private Long id; ... } public class Student extends Person { ... } Another class, Employer, has a bidirectional one-to-many relationship with Worker. public class Worker exten...

sqlalchemy relation through another (declarative)

Is anyone familiar with ActiveRecord's "has_many :through" relations for models? I'm not really a Rails guy, but that's basically what I'm trying to do. As a contrived example consider Projects, Programmers, and Assignments: from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker from sqlalchemy import Column, Fo...

Linq-to-sql Add item and a one-to-many record at once

I have a function where I can add articles and users can comment on them. This is done with a one to many relationship like= "commentId=>ArticleId". However when I try to add the comment to the database at the same time as I add the one to many record, the commentId is not known. Like this code: Comment comment = new Comment(); comment....

unique constraint (w/o Trigger) on "one-to-many" relation

To illustrate the problem, I make an example: A tag_bundle consists of one or more than one tags. A unique tag combination can map to a unique tag_bundle, vice versa. tag_bundle tag tag_bundle_relation +---------------+ +--------+ +---------------+--------+ | tag_bundle_id | | tag_id...

Combining multiple rows into one row, Oracle

Hi. I'm working with a database which is created in Oracle and used in a GIS-software through SDE. One of my colleuges is going to make some statistics out of this database and I'm not capable of finding a reasonable SQL-query for getting the data. I have two tables, one with registrations and one with registrationdetails. It's a one to...

why when I delete a parent on a one to many relationship on grails the beforeInsert event is called on the child??

hello, I have a one to many relationship and when I try to delete a parent that haves more than one child the berforeInsert event gets called on the frst child. I have some code in this event that I mean to call before inserting a child, not when i'm deleting the parent! any ideas on what might be wrong? the entities: class MenuItem {...

NHibernate From One-To-Many to One-To-One

I am creating the security system for the software im creating and I would like to know how i can do the following in NHibernate(if at all possible) User Account Class: public class UserAccount { public virtual int UserID { get; set; } public virtual String Username { get; set; } public virtual Privilege InvoicePrivilege { ...

How to set up a has-many relationship in Cocoa?

I'm building a (very) simple FTP app in Cocoa, and I need to store information on the different types of servers that are supported. So, I've created a ServerType class, which stores all of the relevant information about a single type of server. I then have a ServerTypes class which is designed to manage all of the ServerType classes tha...

What is best practice about having one-many hibernate

Hi all, I believe this is a common scenario. Say I have a one-many mapping in hibernate Category has many Item Category: @OneToMany( cascade = {CascadeType.ALL},fetch = FetchType.LAZY) @JoinColumn(name="category_id") @Cascade( value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN ) private List<Item> items; Item: @ManyT...

One to many too much data returned - MySQL

I have 2 related MySQL tables in a one to many relationship. Customers: cust_id, cust_name, cust_notes Orders: order_id, cust_id, order_comments So, if I do a standard join to get all customers and their orders via PHP, I return something like: Jack Black, jack's notes, comments about jack's 1st order Jack Black, jack's notes, comm...

LINQ to SQL INSERT with one to many relationship

I have two tables - Member and Profile with a one to many relationship. I'm trying to insert into the database using LINQ to SQL but am getting a "The INSERT statement conflicted with the FOREIGN KEY constraint" error. FYI: 1. As this is a practice project to learn LINQ to SQL, I've created my entity classes manually. 2. If I generate t...

Maintaining integrity of Core Data Entities with many incoming one-to-many relationships

Hi all. I have a Core Data store which contains a number of MediaItem entities that describe, well, media items. I also have NewsItems, which have one-to-many relationships to a number of MediaItems. So far so good. However, I also have PlayerItems and GalleryItems which also have one-to-many relationships to MediaItems. So MediaItems a...

DELETE records without associated ones.

I have a 'guests' table and 'invitations' table bound with many-to-one relationship in a postgreSQL database. I have removed some guests and now I want to remove invitations that have no guests. I tried using 'COUNT', but aggregates are not allowed in WHERE clause. ...

PHP Symfony + One-to-Many Relationship + Result Caching

I am getting unexpected behavior (to me!) when defining a one-to-many relationship with Symfony 1.4. Here is a simple example which demonstrates the behavior, having an Employer table and an Employee table: one Employer can have many Employees. The YML schema file is as follows: Employee: columns: id: { type: integer, primary: tru...

mailing system DB structure, need help

i have a system there user(sender) can write a note to friends(receivers), number of receivers>=0. Text of the message is saved in DB and visible to sender and all receivers then they login to system. Sender can add more receivers at any time. More over any of receivers can edit the message and even remove it from DB. For this system i c...