php 使用 Doctrine 和 Symfony2 查询多对多关系
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Query on a many-to-many relationship using Doctrine with Symfony2
提问by Ema.jar
I'm triyng to understand how the many to many relationship works with Doctrine and Symfony2.
我正在尝试了解多对多关系如何与 Doctrine 和 Symfony2 一起工作。
I've recreated the example shown in the official documentation (goo.gl/GYcVE0) and i have two Entity Classes: Userand Groupas you can see below.
我重新创建了官方文档 (goo.gl/GYcVE0) 中显示的示例，并且我有两个实体类：User和Group，如下所示。
<?php
/** @Entity **/
class User
{
// ...
/**
* @ManyToMany(targetEntity="Group", inversedBy="users")
* @JoinTable(name="users_groups")
**/
private $groups;
public function __construct() {
$this->groups = new \Doctrine\Common\Collections\ArrayCollection();
}
// ...
}
/** @Entity **/
class Group
{
// ...
/**
* @ManyToMany(targetEntity="User", mappedBy="groups")
**/
private $users;
public function __construct() {
$this->users = new \Doctrine\Common\Collections\ArrayCollection();
}
// ...
}
If i update my DB i get this MySQL Schema:
如果我更新我的数据库，我会得到这个 MySQL 架构：
CREATE TABLE User (
id INT AUTO_INCREMENT NOT NULL,
PRIMARY KEY(id)
) ENGINE = InnoDB;
CREATE TABLE users_groups (
user_id INT NOT NULL,
group_id INT NOT NULL,
PRIMARY KEY(user_id, group_id)
) ENGINE = InnoDB;
CREATE TABLE Group (
id INT AUTO_INCREMENT NOT NULL,
PRIMARY KEY(id)
) ENGINE = InnoDB;
ALTER TABLE users_groups ADD FOREIGN KEY (user_id) REFERENCES User(id);
ALTER TABLE users_groups ADD FOREIGN KEY (group_id) REFERENCES Group(id);
The problem is that in Symfony2 I need the Entityto generate a query and in this case I don't have an Entity associated to the table users_groupbecause this table is created automatically by the framework.
问题是在 Symfony2 中我需要实体来生成查询，在这种情况下我没有与表关联的实体，users_group因为该表是由框架自动创建的。
So, how can I retrieve the information related to this relationship table? For example I need to get all the Users in a Group which are the users that have an id that appears in the table users_group.
那么，如何检索与此关系表相关的信息呢？例如，我需要获取组中的所有用户，这些用户是具有出现在表中的 id 的用户users_group。
How can I do that using the DQL, QueryBuilder or other methods?
我如何使用 DQL、QueryBuilder 或其他方法来做到这一点？
Thanks a lot.
非常感谢。
回答by M Khalid Junaid
You can write a join DQL query as below
您可以编写一个连接 DQL 查询，如下所示
$em = $this->getContainer()->get('doctrine')->getManager();
$repository = $em->getRepository('YourNamespaceYourBundle:User');
$query = $repository->createQueryBuilder('u')
->innerJoin('u.groups', 'g')
->where('g.id = :group_id')
->setParameter('group_id', 5)
->getQuery()->getResult();
Your mapping for groupsproperty in Userentity will handle join part itself you don't have to mention the junction table in your DQL query
您groups在User实体中的属性映射将自行处理连接部分，您不必在 DQL 查询中提及连接表
