many-to-many

问题 I have 2 models: class Case(models.Model): Priority = ( ('Blocker', 'Blocker'), ('High', 'High'), ('Medium', 'Medium'), ('Low', 'Low'), ) id = models.AutoField(primary_key=True) name = models.CharField(max_length=200) image = models.URLField(blank=True) requirements = models.URLField(blank=True) priority = models.CharField(max_length=10, choices=Priority) description = models.CharField(max_length=200) step = models.TextField() modified = models.DateTimeField(editable=False) user = models

问题 I have 2 entities: 1) User 2) Department. each contains a SET of the other since the relationship between them is manyToMany, I marked (CascadeType.ALL) on the user entity and the department entity and when i do : userX.getDepartments.remove(departmentX); save(userX); it works like intended - it actually implies that departmentX.getUsers.contains(userX) == false. is called implicitly. BUT , when i do departmentY.getUsers.remove(userX); save(departmentY); it doesn't cascade! meaning - i can do

问题 I am currently working on a project that has recently acquired many database records. I now am trying to optimize for this. Here are my models: public class QueueEntity { public int Id { get; set; } public string Name { get; set; } public virtual List<PhraseEntity> Phrases { get; set; } } public class PhraseEntity { public int Id { get; set; } public string Name { get; set; } public virtual SourceEntity Source { get; set; } public virtual List<QueueEntity> Queues { get; set; } } public class

问题 models.py: class Tag(models.Model): name = models.CharField(max_length=100) description = models.CharField(max_length=500, null=True, blank=True) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now_add=True) class Post(models.Model): user = models.ForeignKey(User) tag = models.ManyToManyField(Tag) title = models.CharField(max_length=100) content = models.TextField() created = models.DateTimeField(default=datetime.datetime.now) modified = models

问题 I have a question. I use JPA with eclipselink and I have relationship: Table A ---< Table AB >---- Table B class A { @OneToMany(mappedBy = "a") private List<AB> abList } class AB { @ManyToOne(fetch = FetchType.LAZY) private A a; @ManyToOne(fetch = FetchType.LAZY) private B b; } class B { @OneToMany(mappedBy = "b") private List<AB> abList; } It is ManyToMany relationship between A and B with join table AB. Now I want to remove a record from table A and to cascade remove records from table AB

问题 I'm building a personal blog app with Entity Framework 4 CTP 5 POCO only, where a Post can have many Tags and a Tag can be in many Posts . My question is whether to build a many-to-many model, or to have a lookup table. At first I was trying to use many-to-many, but I don't know how to do insertion, each time a new post is posted (with many tags selected), I'm not sure what to do so that the tags should be associated with the post (and wouldn't insert a new tag if the tag name already exists.

问题 I do have swatches table, a colors table and a swatch_color pivot table. Relations are set as: public function colors() { return $this->belongsToMany('Color'); } public function swatches() { return $this->belongsToMany('Swatch'); } I have no problem to retrieve the swatches with the color relations $swatches = Swatch::with('colors')->get(); return dd($swatches); Colors is always an array of 5 color objects with hue, R, G, and B attributes. Now I would like to sort the swatches by the R value

问题 I have two Django models with are related to each other through a many-to-many relationship. I need to list the cross product of both tables. Let say for simplicity's sake that the two models are Pizza and Topping. I would like the query to return something like this: pizza_name topping --------------------- all dressed cheese all dressed mushrooms all dressed onions all dressed peperoni all dressed pepper reddit cheese reddit peperoni reddit bacon reddit baconbits The amount of data will be

问题 I am trying to implement user management functionality for a web site. I am using ASP.NET MVC 3, Entity Framework 4.1, MvcScaffolding. Let's consider the entities: The user entity: public class User { public int Id { get; set; } public string FirstName { get; set; } public string LastName { get; set; } public virtual ICollection<UserGroup> Groups { get; set; } } The user group entity: public class UserGroup { public int Id { get; set; } public string Name { get; set; } public virtual

问题 In my current project (which is really small) i have 3 tables/ POCO entities which i would like to manipulate using EF. The Tables are: Status (contains status details) StatusStatusType (which is needed because of the many-2-many relationship) StatusType (A table which is used to group statuses by type) I now want to create a new Status in the database and user code like you see below //Create new status (POCO) entity var newStatus = new Status { StatusId = status.Id, UserId = user.Id, Text =