I have two models with a many to many relationship using has_and_belongs_to_many. Like so: class Competition < ActiveRecord::Base has_and_belongs_to_many :teams accepts_nested_attributes_for :teams end class Team < ActiveRecord::Base has_and_belongs_to_many :competitions accepts_nested_attributes_for :competitions end If we a...
hi i have a many to many relationship between a user and a group.and i will like to add a user with many groups in my database.how do i do that if my database is as follows user_group_table = Table('tg_user_group', metadata, Column('user_id', Integer, ForeignKey('tg_user.user_id', onupdate="CASCADE", ondelete="CASCADE")), ...
I'm new to Entity Framework and am trying to figure things out. I have a database created that's not very complicated. There's about 7 tables and 3 of those are mapping tables to associate one table record w/ another. The example I'm using here is this: Table User UserId UserName Table Role RoleId RoleName Table: UserRole UserI...
Can anyone point out a good many-to-many database tutorial for CodeIgniter. Just trying to work out the process of creating, and then updating a many-to-many relationship. My example uses a multi-select of values, wondering how you take care of monitoring changes on update etc. ...
All previous attempts at a JOIN have left me with either the disc or item data populating the id, title keys of the result (maybe a clash is occuring). So I have: item table fields: id, title disc table fields: id, title item_disc table fields: item_id, disc_id How do I construct a double join so that I can access the related discs...
I'm a hibernate newbie and I'm not entirely sure how to get the cascade behavior I'm looking for. Let's say I have two classes A and B with bi-directional many-to-many mappings to each other. A is the owner side and B is the inverse side (I hope I have the terminology correct). public class A { private Set<B> bSet = new HashSet<B>(...
I have a many to many relationship in Django similar as this: class Account ( models.Model ): name = models.CharField( max_length = 30 ) user = models.ForeignKey( User, null = True, blank = True ) class Publisher ( models.Model ): publisherID = models.BigIntegerField( ) name = models.CharField( max_length = 30 ) lastRequested...
I'm trying to map a @ManyToMany association using hibernate. But so far I only managed to have cascade on one of the foreign keys. My source code goes like this: @Entity public class Airplane { @Id @GeneratedValue(strategy=GenerationType.AUTO) private Long id; @OnDelete(action=OnDeleteAction.CASCADE) @ManyToMany(m...
I am using MySQL (MyISAM) 5.0.41 and I have this query: SELECT `x`.`items`.id, `x`.`items`.name, COUNT(*) AS count FROM `x`.`items` INNER JOIN `x`.`user_items` ON `x`.`items`.id = `x`.`user_items`.item_id GROUP BY name HAVING count > 2 ORDER BY count DESC I have about 36,000 users, 175,000 user_items and 60,000 items which...
I have a table that holds products, another that holds variations and a third that hold product variations (many products can have many variations..both ways). I want to display (group by) each product and show the variations. what i've read is just looping thru and comparing id's to see which record you are on, if a new one then adjus...
In Django, I've got a Checkout model, which is a ticket for somebody checking out equipment. I've also got an OrganizationalUnit model that the Checkout model relates to (via ForeignKey), as the person on the checkout belongs to an OrganizationalUnit on our campus. The OrganizationalUnit has a self relation, so several OUs can be the ch...
Hi All, I have a models in Django that are something like this: class Classification(models.Model): name = models.CharField(choices=class_choices) ... class Activity(models.Model): name = models.CharField(max_length=300) fee = models.ManyToManyField(Classification, through='Fee') ... class Fee(models.Model): activity = m...
I have a many to many relationship in rails. All database tables are named accordingly and appropriately. All model files are plural and use underscore to seperate words. All naming comventions are followed by ruby and rails standards. I'm using has many through in my models like this: has_many :users, :through => :users_posts #Post...
Hello, I've a problem with saving changes to database, I'm using LINQ2SQL mapping. I've implemented M:M relation (User <= UserRole => Role) based on tutorial: http://www.codeproject.com/KB/linq/linqtutorial2.aspx#premain25 Everything works fine when I'm using one class which is inherits from DataContext and is responsible for all of m...
I have 3 tables: Companies, Subcontracts, and CompanyToSubcontract The CompanyToSubcontract table is the guid of the Company and guid of the Subcontract. I have a MultiSelectList on the Subcontract Edit and Create views where the user can select multiple companies. I finally got it working where it displays the correct companies as se...
OK, so here is the problem. Its not even as crazy as the guy who wants to map m:n with different column counts in his PKs. No matter what I do or where I look there seems to be no method chain that will result in a successful mapping of this. I have tried doubling up on the Parent and Child columns, eg ParentColumn("").ParentColumn(""...
I have 3 tables Subcontract, Company, and a link table CompanyToSubcontract. The link table contains the Subcontract_id and the Company_id. The foreign keys were set-up in SQL and when I drug them into my dbml the one-to-many relationship arrows showed up and everything looked fine. However, when coding, it's as if the relationship is...
This question comes up after reading a comment in this question: http://stackoverflow.com/questions/2190089/database-design/2190101 When you create a many-to-many table, should you create a composite primary key on the two foreign key columns, or create a auto-increment surrogate "ID" primary key, and just put indexes on your two FK co...
Im using the Repository pattern and I want to write a method that receives a role and returns an Iqueryable of the users that belong to that role. (Im not sure if the right way would be to receive the role object or the role_id... in any case, how can I do this?? I dont like the query structure, I prefer the method structure of linq. use...
Hi - I have a ModelForm in my Django app that uses a forms.ModelMultipleChoiceField, which displays as a forms.CheckboxSelectMultiple widget on the form. This ModelForm is used to select/de-select values for a many-to-many relation. Here's the problem: when you uncheck all of the checkboxes and save the form, it doesn't save. If you un...