学说：让所有孩子成为多对多的关系

Question

I need a single DQL query that would return all posts for a given tag.

posts and tags have a many-to-many relation, s given a tag.slug I should be able to get all posts related to that tag, but how?

UPDATE:

I'm using Doctrine 2.1 with Symfony 2, my entities look like this:

/**
 * @ORM\Entity
 * @ORM\Table(name="articles__posts")
 */
class ArticlePost
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\ManyToMany(targetEntity="ArticleTag", inversedBy="posts")
     * @ORM\JoinTable(name="articles__posts_tags")
     */
    protected $tags;
}

/**
 * @ORM\Entity
 * @ORM\Table(name="articles__tags")
 * @UniqueEntity(fields="slug")
 */
class ArticleTag
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\ManyToMany(targetEntity="ArticlePost", mappedBy="tags")
     */
    protected $posts;
}

Answer 1

If you only want to search with one tag, try this:

SELECT post FROM ArticlePost post
JOIN post.tags tag
WHERE tag.slug = {$tagSlug}

If you want to search by more than one tag, simply change the condition to:

... WHERE tag.slug IN ( {$slug1}, {$slug2}, ... {$slugN} )