foreign-key-relationship

Not sure if I'm reading this right, but it seems like Scaffold will not do a one-to-many relationship in its entirety. For instance, if I create messages with scaffold and then I want comments on those messages (one message -> many comments ), I have to go through and change everything. For instance, I have to change this in the comment 's new view <% form_for(@comment) do |f| %> to this <% form_for([@message, @comment]) do |f| %> and then change the Action to set up the @message var... amongst other things. This cannot currently be done automatically with Scaffold, right? This is true, but,

I have a couple of models: class Customer(models.Model): customer_name = models.CharField(max_length=200) def __unicode__(self): return self.customer_name class Meta: ordering = ('customer_name',) class Unit(models.Model): unit_number = models.IntegerField() rentable = models.BooleanField() owner = models.ForeignKey(Customer, related_name='units', blank=True, null=True) def __unicode__(self): return str(self.unit_number) class Meta: ordering = ('unit_number',) I have the admin interface working fine when I'm adding a unit (I can select which customer to assign it to) but when I go to create

i know you will say that this question is asked before many times but i havent solved it yet... models.py class Doc(UploadModel): doc_no = models.CharField(max_length=100, verbose_name = "No", blank=True) date_added = models.DateTimeField(verbose_name="Date", default=datetime.now, editable=False) class DocImage(models.Model): property = models.ForeignKey(Doc, related_name='images') image = FileBrowseField("Docs", max_length=200, directory="doc_img/%Y/%m/%d/%H/%M/%S/", extensions=[".jpg",".tif"], blank=True, null=True) views.py def doc_detail(request, dosc_no): res = Doc.objects.filter(doc_no =

This question is pretty much similar to this one , but for SQL Server 2005 : I have 2 tables in my database: --'#' denotes the primary key [Libraries] #ID #Application Name 1 MyApp Title 1 2 MyApp Title 2 [Content] #ID Application LibraryID Content 10 MyApp 1 xxx 11 MyApp 1 yyy (the database is obviously much more complex and having this double key makes sense) Each library is identified by its unique ID and Application name. I'm trying to ensure that each content is properly referencing an existing library. When creating the constraint (using the Wizard) as Primary key table Foreign key table

I have the same problem as in the following post . So I am wondering, why doesn't Rails support generating foreign keys by default? Isn't it necessary? Or are we supposed to do it manually? Database constraints aren't required any more than wearing seat-belts are required in your car. You can drive around all you like and everything will work great until a problem arrives. The seat-belt (constraints) keep you (the data) safe. So it's highly recommended that you create constraints to enforce data-integrity at the database level, because it's highly likely that 1) You will interact with the

I have two tables Books and Audiobooks, both of which have ISBN as their primary keys. I have a table writtenby that has an isbn attribute that has a foreign key constraint to Books and Audiobooks ISBN. The issue that comes up when I insert into writtenby is that postgresql wants the ISBN I insert into writtenby to be in both Books and Audiobooks. It makes sense to me to have a table writtenby that stores authors and the books/audiobooks they have written, however this does not translate to a table in postgresql. The alternative solution I am thinking of implementing was having two new

It's been almost a week since I've began to dig deeper in forms , associations , hashes , symbols... But it seems I cannot solve the puzzle without your help . I am working on a project for displaying different galleries content . The basic idea is when the user sees the names of galleries (names are links ) to be able to click on chosen one. Then all the images ,that belong to this gallery , are displayed . On the bottom there should be a link "Add image in this gallery" . My models : class Gallery < ActiveRecord::Base attr_accessible :name has_many :pictures end class Picture < ActiveRecord:

Customers customer_id Orders order_id customer_id fk If I have two tables and define a foreign key on customer_id in the Orders table, by allowing it to be null I am saying that I can have an order that does not have a customer associated with it. As such, the notion of a nullable foreign key seems at odds with the purpose of a foreign key, which is to enforce this constraint. Is there a simple example of a situation in which a nullable foreign key would be necessary? Or an argument in favor of permitting them? Imagine a table that holds the TODOs of a team. If a TODO is not yet assigned to a