relationship

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have the following 3 classes: class Resource: id = Column(Integer, primary_key=True) path = Column(Text) data = Column(Binary) type = Column(Text) def set_resource(self, path, data, type): self.path = path self.data = data self.type = type class EnvironmentResource(Base, Resource): __tablename__ = 'environment_resources' parent_id = Column(Integer, ForeignKey('environments.id', ondelete='CASCADE')) def __init__(self, path, data, type): self.set_resource(path, data, type) class Environment(Base): __tablename__ = 'environments' id = Column

It took me a while, but I figured out how to use SQLAlchemy to model a relationship across two different kinds of databases: Base = declarative_base() class Survey(Base): __tablename__ = 'SURVEY' survey_id = Column("SURVEY_ID", Integer, primary_key=True) term_id = Column("TERM_ID", Integer, nullable=False) # Because the TERM table is in Oracle, but the SURVEY table is in # MySQL, I can't rely on SQLAlchemy's ForeignKey. Thus, # I need to specify the relationship entirely by hand, like so: term = relationship("Term", primaryjoin="Term.term_id==Survey.term_id", foreign_keys=[term_id], backref=

In an event handler for a Command for a DataGrid, I get DataGridCell in ExecutedRoutedEventArgs. However, I couldn't figure out how to get its associated DataGrid and DataGridRow. Your help is much appreciated. You probably want to set some sort of RelativeSource binding that can get you the "parent grid/row" via a {RelativeSource FindAncestor, AncestorType={x:Type DataGrid}} , but your question got me thinking... You could: Use Reflection: var gridCell = ....; var parentRow = gridCell .GetType() .GetProperty("RowOwner", BindingFlags.NonPublic | BindingFlags.Instance) .GetValue(null) as

I'm developing a web API with Laravel 5.0 but I'm not sure about a specific query I'm trying to build. My classes are as follows: class Event extends Model { protected $table = 'events'; public $timestamps = false; public function participants() { return $this->hasMany('App\Participant', 'IDEvent', 'ID'); } public function owner() { return $this->hasOne('App\User', 'ID', 'IDOwner'); } } and class Participant extends Model { protected $table = 'participants'; public $timestamps = false; public function user() { return $this->belongTo('App\User', 'IDUser', 'ID'); } public function event() {

I have 300+ classes. They are related in some ways. For simplicity, all relation are 1:1. Here is a sample diagram. (In real case, there are around 50 relation-pairs.) Note: For some instances, some relation may not exist. For example, some hen s don't relate to any food . Note2: No link = never, e.g. every egg doesn't relate to any cage . Such relation will never be added/removed/queried. Question: How to store relation between them elegantly? All 4 of my ideas (below) seem to have disadvantages. Here is a related question but with 1:N and only 1 relation. My poor solutions These are semi

What inverse_of does mean in mongoid associations? What I can get by using it instead of just association without it? In a simple relation, two models can only be related in a single way, and the name of the relation is automatically the name of the model it is related to. This is fine in most cases, but isn't always enough. inverse_of allows you to specify the relation you are referring to. This is helpful in cases where you want to use custom names for your relations. For example: class User include Mongoid::Document has_many :requests, class_name: "Request", inverse_of: :requester has_many

I have two models, users and promotions. The idea is that a promotion can have many users, and a user can have many promotions. class User < ActiveRecord::Base has_and_belongs_to_many :promotions end class Promotion < ActiveRecord::Base has_and_belongs_to_many :users end I also have a promotions_users table/model, with no id of its own. It references user_id and promotions_id class PromotionsUsers < ActiveRecord::Base end So, how do I add a user to a promotion? I've tried something like this: user = User.find(params[:id]) promotion = Promotion.find(params[:promo_id]) promo = user.promotions

I know this question is asked by many people already for my research, here's some questions asked before How to delete all relationships in neo4j graph? https://groups.google.com/forum/#!topic/neo4j/lgIaESPgUgE But after all, still can't solve our problems, we just want to delete "ALL" nodes and "ALL" relationships suppose delete "ALL" can see there are left 0 nodes 0 properties and 0 relationships This is the screenshot i took after executing the delete "ALL" suggested by forum My question still the same, how do delete all nodes and all relationships in neo4j Bob B As of 2.3.0 and up to 3.3.0

I have a table of persons. Each person has a property and many persons may have a certain property. So this is a many-to-many relationship. This is the schema: CREATE TABLE persons ( person_id int(11) NOT NULL AUTO_INCREMENT, firstname varchar(30) NOT NULL, lastname varchar(30) NOT NULL, PRIMARY KEY (person_id) ); CREATE TABLE properties ( property_id int(11) NOT NULL AUTO_INCREMENT, property varchar(254) NOT NULL UNIQUE, PRIMARY KEY (property_id) ); CREATE TABLE has_property ( person_id int(11) NOT NULL, property_id int(11) NOT NULL, PRIMARY KEY (person_id,property_id), FOREIGN KEY (person_id