many-to-many

问题 Background In a PostgreSQL 9.0 database, there are various tables that have many-to-many relationships. The number of those relationships must be restricted. A couple of example tables include: CREATE TABLE authentication ( id bigserial NOT NULL, -- Primary key cookie character varying(64) NOT NULL, -- Authenticates the user with a cookie ip_address character varying(40) NOT NULL -- Device IP address (IPv6-friendly) ) CREATE TABLE tag_comment ( id bigserial NOT NULL, -- Primary key comment_id

问题 I'm looking for the optimal solution for keyword matching between different records in the database. It's a classic problem, I've found similar questions, but nothing concretely. I've done it with full text searches, joins and subqueries, temp tables, ... so i'd really like to see how you guys are solving such a common problem. So, let's say I have two tables; Products and Keywords and they are linked with the third table, Products_Keywords in a classic many-to-many relationship. If I show

问题 Struggling with an issue in Laravel 4, in a "contact" model edit form, I can get all fields current values except those from the multiple select which is to establish a relation with another model "company". It's a many-to-many relationship. I'm getting the list of companies, but none are selected even if a relation exists. Here's my edit form: {{ Form::model($contact, array('route' => array('crm.contacts.update', $contact->id), 'id' => 'edit-contact')) }} <div class="control-group"> {{ Form:

问题 In a relational DB, I could have a table Person and a table Hobby . Every person can have zero, one or more hobbies , and I also want to record, say, the priority of those hobbies for every person . I could create a relationship table with the 2 foreign keys PersonFK and HobbyFK , and one plain column Priority . In datomic, to model a simple n:m relationship (without the priority), I'd probably create an attribute of type Reference with cardinality Many , that I'd use for Person entities. But

问题 I can lazy load one-to-many and many-to-one associations but I can't with the many-to-many associations. We have a city in wich we have merchants wich have adresses. Merchants can have multiple addresses and multiple merchants can have the same addresses. When we load a merchant with a get, Merchant merchant = (Merchant) hib_session.get(Merchant.class, id); System.out.println(merchant.getName()); it's ok, addresses aren't load until we iterate over them. But when we load a list of merchants,

问题 I have Peticion entity but something is missing because appears the following error: No identifier/primary key specified for Entity (...) Every Entity must have and identifier/primary key This is the entity code: <?php namespace Project\UsuarioBundle\Entity; use Doctrine\ORM\Mapping as ORM; /** * Peticion * * @ORM\Table(name="peticion") * @ORM\Entity */ class Peticion { /** * * @ORM\Id * @ORM\ManyToMany(targetEntity="Project\UsuarioBundle\Entity\Usuario", inversedBy="usuNick2") * @ORM

问题 I am looking for the best way to handle a database of many-to-many relationships in PHP and MySQL. Right now I have 2 tables: Users (id, user_name, first_name, last_name) Connections (id_1, id_2) In the User table id is auto incremented on add and user_name is unique, but can be changed. Unfortunately, I don't have control over the user_name and its ability to be changed, but I must account for it. The Connections table is obviously, user1 and user2's id. The connection table needs to account

问题 I'm working on my first project with RoR and I need to create many to many relationship between two models but with possibility of ordering objects of first model in association to second model. Let's say that I have two following models - Customer - Route I want assign many Customers to many Routes but with storing order of this association, so for example -Route 1 --Customer 2, position 1 --Customer 1, position 2 -Route 2 --Customer 3, position 1 --Customer 1, position 2 I think I have to

问题 Each user has a list of roles: <class name="User" lazy="false" table="Users"> <id name="Id" type="int"> <generator class="native"/> </id> <property name="Name" /> <bag name="RoleList" table="User_Role" inverse="true" lazy="false" collection-type="Roles"> <key column="UserId" foreign-key="Id"/> <many-to-many class="Role" column="RoleId"/> </bag> </class> I am tracking all the queries to the SQL server. When I select user, I also see the SQL SELECT statement (which is Ok). The problem is when I

问题 I have a DB with the following relationships: A <<-->> B A: Members table; B: Activities table A Member has many Activities, and each Activity has many Members. So, a many to many relationship. When the user selects an Activity from a tableView, a new tableView should be pushed with all the Members that has that Activity. In the NSPredicate of the "child" tableView, I do: request.entity = [NSEntityDescription entityForName:@"Members" inManagedObjectContext:context]; request.predicate =