foreign-keys

Database design w/Entity Framework 4 - where should I put my foreign keys?

I'm developing a couple of media (video games, TV shows, movies) review sites and am having an issue designing the relationships between my data. Case in point: I decided that having a base Content table would be a good idea for most of the data. My Articles, News, and Reviews tables could all point to the Content table. My current s...

How to implement ONE-TO-MANY in a database.

I want to implement one-to-many concept in my application. This is the scenario, i have two tables (i). Person(ID, NAME, AGE, DEPT) (ii). Person Responsibilities(ID, RESP'S). One person may have more than one resp's. How shall i implement 1-n Relationship here. Actually, i cant able to understand the correct concept of this. Any s...

What are the design criteria for primary keys?

Choosing good primary keys, candidate keys and the foreign keys that use them is a vitally important database design task -- as much art as science. The design task has very specific design criteria. What are the criteria? ...

Foreign key problem in Java Persistance API with Netbeans 6.9.1

Hi All, I have an error in setting up Java Persistence in Netbeans. I have used MySQL as Back-End Database Server. My Code is as below, Database CREATE TABLE `hub` ( `hub_ID` INT(11) NOT NULL AUTO_INCREMENT, `hub_Name` VARCHAR(45) NOT NULL, PRIMARY KEY (`hub_ID`), UNIQUE INDEX `hub_Name` (`hub_Name`) )ENGINE=MyISAM CREATE TABLE...

fluent-nhibernate automapping foriegn key inserts null.

I have a class called Worker public class Worker : BaseEntity { public virtual int WorkerID { get; set; } public virtual string Name { get; set; } public virtual IList<Indemnification> Indemnifications { get; set; } } public class Indemnification : BaseEntity { public virtual int IndemnificationID { get; set; } pu...

Surrogate foreign key

Oki so I have two tables: person and person_email PERSON ------ id (PK) person_code (Unique key 1) person_type (Unique key 1) surname forename PERSON_EMAIL ------------ id (PK) person_id (Unique key 1) (references person(id)) email_address (Unique key 1) Is this correct?? or should it be: PERSON_EMAIL ------------ id (PK) person_i...

mysql query help, getting values from table using relational id's from another table

THE SQL THAT BUILDS THE TABLES, -- -- Table structure for table `careers` -- CREATE TABLE IF NOT EXISTS `careers` ( `career_id` int(11) NOT NULL auto_increment, `career_name` varchar(75) NOT NULL, `career_desc` text NOT NULL, `degree_needed` enum('Yes','No') NOT NULL, `useful_info` text, `useful_links` text, PRIMARY K...

Optional foreign key with django?

Hi, In my models I want to have an optional field to a foreign key. I tried this: field = models.ForeignKey(MyModel, null=True, blank=True, default=None) But i am getting this error: model.mymodel_id may not be NULL i am using sqlite edit: if it can help, here is the exception location: /usr/lib/python2.6/site-packages/django/d...

Hibernate: Where do insertable = false, updatable = false belong in composite primary key constellations involving foreign keys?

When implementing composite primary keys in Hibernate or other ORMs there are up to three places where to put the insertable = false, updatable = false in composite primary key constellations that use identifying relationships (FKs that are part of the PK): Into the composite PK class' @Column annotation (@Embeddable classes only) or I...

Django models.py Circular Foreign Key

I have a django app which basically is just a photo album. Right now I have two models: Image and Album. Among other things, each Album has a foreign key to an Image to be its thumbnail and each Image has a foreign key to the Album it belongs in. However, when I try to use manage.py syncdb or manage.py sqlall I get errors saying the clas...

Django - Multiple columns primary key

Hello, I would like to implement multicolumns primary keys in django. I've tried to implement an AutoSlugField() which concatenate my columns values(foreignkey/dates) ... models.py : class ProductProduction(models.Model): enterprise = models.ForeignKey('Enterprise') product = models.ForeignKey('Product') date = models.Dat...

Upgrade the version sqlite3 used by xcode?

I wish to use the foreign keys facility, and thus upgraded my version of sqlite to the latest stable version 3.7.2. I've verified the version in terminal by entering in: > whereis sqlite3 = /usr/bin/sqlite3 > sqlite3 --version = 3.7.2 Now, when I come to create a new database using FireFox's SQL Manager plugin it reports it is using...

Rails Single Table Inheritance using Foreign Key (ID)

Hi, I have to model an association structure and the association is divided into divisions/subdivisions/sections etc. So I've created a simple Entity-Attribute Model: I'd like to use rail's single-table-inheritance but it seems like this works only if the type column is a string. My question is how to achieve this with my approach? S...

Foreign Key relations in Django, with a select condition

I've a table of partner type PartnerType Name Description RelatedToProject I've a PartnerMaster Name Address PartnerType I've a Project Table Name Partner (from partner master) The partner in the project table has to be only of those types who have RelatedToProject = True How can I achieve this in the model definition itself. ...

How can we set tables relations in SQL Server Express?

I have SQL Server Express 2008. How can I set a table's relations in it? ...

Check if a row could be deleted in MySQL

Is there a way I can check if a row potentially could be deleted? That it for example is not currently connected through restricted foreign keys to anything else. Reason: I am making an admin page with all the users in the system listed. They can always be disabled, but they may also be deleted. However they can only be deleted if they...

How can I INSERT data into two tables simultaneously in SQL Server?

Let's say my table structure looks something like this: CREATE TABLE [dbo].[table1] ( [id] [int] IDENTITY(1,1) NOT NULL, [data] [varchar](255) NOT NULL, CONSTRAINT [PK_table1] PRIMARY KEY CLUSTERED ([id] ASC) ) CREATE TABLE [dbo].[table2] ( [id] [int] IDENTITY(1,1) NOT NULL, [table1_id] [int] NOT NULL, [data] [v...

Which foreign key to use in a many-to-one table

Suppose I have a table Books with columns Book_ID (Primary Key), ISBN (Unique), and several others such as Title/author/etc. I have another table Sales, with primary key Sale_ID, a foreign key to link to Books, and other fields with info on Sales. Sales only exist for books with ISBNs. Is it better database design to have Book_ID or I...

Having serious problems with Entity Framework & Foreign Keys :(

Hi folks, I've got the following entities on my EDMX :- These two entites were generated by Update Model From Database. Now, notice how my country has the following primary key :- Name & IsoCode this is because each country is UNIQUE in the system by Name and IsoCode. Now, with my States ... it's similar. Primary Key is :- Name ...

Why does postgreSQL check foreign key constraints twice?

I have a postgresql database with two tables, one which has a foreign key constraint which references the other. The constraint is set to cascade on update and delete, so an update on the referenced table should cascade to the referencing table. When I analyzed an update on the referenced table, using explain analyze the I got the follow...