DQL多对多,数不胜数

Question

我正在使用带有Doctrine的Symfony 2,并且我有两个实体加入了多对多关联.假设我有两个实体:User和Group,db上的相关表是users,groups和users_groups.

我想在DQL中获得前十大人口最多的组,但我不知道在连接表(users_groups)上执行查询的语法.我已经查看了Doctrine手册,但我没有找到解决方案,我想我还有很多东西可以学习DQL.

在普通的SQL中,它将是:

select distinct group_id, count(*) as cnt from users_groups group by group_id order by cnt desc limit 10

你能帮我把它翻译成DQL吗？

更新(课程):

/**
 * Entity\E_User
 *
 * @ORM\Table(name="users")
 * @ORM\Entity
 */
class E_User
{
    /**
     * @ORM\ManyToMany(targetEntity="E_Group", cascade={"persist"})
     * @ORM\JoinTable(name="users_groups",
     *      joinColumns={@ORM\JoinColumn(name="user_id", referencedColumnName="id", onDelete="cascade")},
     *      inverseJoinColumns={@ORM\JoinColumn(name="group_id", referencedColumnName="id", onDelete="cascade")}
     * )
     */

    protected $groups;

    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @var string $name
     *
     * @ORM\Column(name="name", type="string", length=255)
     */
    private $name;

    /* ... other attributes & getters and setters ...*/
}


/**
 * Entity\E_Group
 *
 * @ORM\Table(name="groups")
 * @ORM\Entity
 */
class E_Group
{
    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @var string $name
     *
     * @ORM\Column(name="text", type="string", length=255)
     */
    private $name;

    /* ... other attributes & getters and setters ...*/
}

Answer 1

如果没有看到实际的类,这并不容易,但通过猜测你有一个多对多的双向关系:

$dql = "SELECT g.id, count(u.id) as cnt FROM Entity\Group g " .
    "JOIN g.users u GROUP BY g.id ORDER BY cnt DESC LIMIT 10;";
$query = $em->createQuery($dql);
$popularGroups = $query->getArrayResult();

更新:

你不用必须使用一个双向的关系,你可以查询的其他方式:

$dql = "SELECT g.id, count(u.id) as cnt FROM Entity\User u " .
    "JOIN u.groups g GROUP BY g.id ORDER BY cnt DESC LIMIT 10;";