many-to-many

I have a couple of models in django which are connected many-to-many. I want to create instances of these models in memory , present them to the user (via custom method-calls inside the view-templates) and if the user is satisfied, save them to the database. However, if I try to do anything on the model-instances (call rendering methods, e.g.), I get an error message that says that I have to save the instances first. The documentation says that this is because the models are in a many-to-many relationship. How do I present objects to the user and allowing him/her to save or discard them

I'm currently having problems with a n:n relationship with Laravel 4, I'm having an error wiht pivot table which is quering on a table with with both components on singular name. I create a pivot table lands_objs and populate it: Models are: <?php class Obj extends Eloquent { protected $guarded = array(); public static $rules = array(); public $timestamps = false; public function land() { return $this->belongsToMany('Land'); } <?php class Land extends Eloquent { protected $guarded = array(); public static $rules = array(); public $timestamps = false; public function objs() { return $this-

I have a many to many relationship setup in a Flask app in SQLAlchemy using a Association Object. I then have have assocation proxies setup between the the classes, to give more direct access rather than going via the association object. Here is an abbreviated example of the setup: class Person(Model): __tablename__ = 'persons' id = Column(Integer, primary_key=True) last_name = Column(Text, nullable=False) groups = association_proxy('group_memberships', 'group') # Other stuff class Group(Model): __tablename__ = 'groups' id = Column(Integer, primary_key=True) name = Column(Text, nullable=False)

My models contain a many-to-many relationship. Measurements can be part of any number of DataSets . # models.py from django.db import models class DataSet(models.Model): purpose = models.TextField() class Measurement(models.Model): value = models.IntegerField() sets = models.ManyToManyField(DataSet, null=True, blank=True, verbose_name="datasets this measurement appears in") I want my admin interface to inlines Measurement fields in the DataSet admin like how a TabularInline works with a ForeignKey field. This is what I have so far: # admin.py from django.contrib import admin from myapp.models

Consider the following models: class Person(models.Model): name = models.CharField(max_length=128) class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64) Membership is a customized many-to-may through object with extra fields. If I have a person instance, how can I access the corresponding date_joined fields of all its membership relations -

I am using the entity framework and modelling a many-to-many relationship. I have created the relationship between the two entities using the fluent API (let's say users and groups): this.HasMany(t => t.Users) .WithMany(t => t.Groups) .Map( m => { m.ToTable("GroupMembers"); m.MapLeftKey("Group_Id"); m.MapRightKey("User_Id"); }); This works great, but I'd like to also be able to reference the GroupMembers table directly. To do that, I have something like: [Table("GroupMembers")] public class GroupMember { #region Properties /// <summary> /// Gets or sets the group. /// </summary> public virtual

This question is based on the thread . If we have one-to-many data structure, we need to have a "help-table" to store for instance phonenumbers for one person. Many person cannot have the same phonenumbers. I look forward for an explanation why we then need two "help-tables" between many-to-many relations. An example of this is a question-site where many users can add the same tags: alt text http://files.getdropbox.com/u/175564/db/db-55.png Why do we need to have the tables Question-Tag-xref and Question-Tags ? Why cannot we just have one table for tags as follows? Question_id | tag 1 C 1 C++