如何在内部连接表上应用DISTINCT

Question

I have the following entity, basically it says a picture has a shop

class InstagramShopPicture
{

   /**
     * @Exclude()
     * @ORM\ManyToOne(targetEntity="InstagramShop", inversedBy="userPictures")
     * @ORM\JoinColumn(name="shop_id", referencedColumnName="id", nullable=false, onDelete="CASCADE")
     */
    protected $shop;

}

how do I query 10 pictures, each from a unique store in DQL?

So far I have the following:

 $query = $em->createQueryBuilder()->select('picture')
               ->from("ShopiousMainBundle:InstagramShopPicture", 'picture')
               ->innerJoin('picture.shop', 'shop')
               ->setMaxResults(10);
                    ;

in other words I just wanted DISTINCT shop, but I am finding it hard to transalate DISTINCT into DQL

UPDATE:

$query = $em->createQueryBuilder()
                    ->select('pictures')
                    ->from("AppMainBundle:InstagramShop", 'shop')
                    ->innerJoin('shop.userPictures', 'pictures')
                    ->innerJoin('pictures.category', 'category')
                    ->innerJoin('category.pictureFirstLevelCategory', 'firstLevelCategory')
                    ->distinct()
                    ;

        $query->andWhere('firstLevelCategory = :firstLevelCategory');
        $query->andWhere('shop.isLocked = false');
        $query->andWhere('shop.expirydate IS NOT NULL');
        $query->andWhere('shop.id != :shopId');
        $query->andWhere('shop.expirydate >= :currentDate');

        $parameter["currentDate"] = new \DateTime('now');
        $parameter["shopId"] = $shopId;
        $parameter["firstLevelCategory"] = $picture->getCategory()->getPicturefirstlevelcategory()();

I tried doing the above and it gives me this error:

Error: Cannot select entity through identification variables without choosing at least one root entity alias.

UPDATE:

SELECT DISTINCT pictures FROM AppMainBundle:InstagramShop shop INNER JOIN shop.userPictures pictures INNER JOIN pictures.category category INNER JOIN category.pictureFirstLevelCategory firstLevelCategory WHERE firstLevelCategory = :firstLevelCategory AND shop.isLocked = false AND shop.expirydate IS NOT NULL AND shop.id != :shopId AND shop.expirydate >= :currentDate