错误:如果不选择至少一个根实体别名，则无法通过标识变量选择实体

我正在我的存储库中使用此查询构建器：

public function findByCityCategory($city, $category)
{
    $qb = $this->createQueryBuilder('e')
        ->select(['e.id','e.title','e.address', 'e.lat', 'e.lng', 'e.siteUrl', 'e.phoneNo', 'w', 'd.id as category', 'avg(r.rating) as rating'])
        ->innerJoin('e.workingTimes', 'w')
        ->innerJoin('e.category', 'd')
        ->where('d.id = :categoryId')
        ->andWhere('e.city = :cityId')
        ->leftJoin('e.ratings', 'r')
        ->groupBy('r.place')
        ->setParameter('categoryId', $category)
        ->setParameter('cityId', $city);
    return $qb->getQuery()->getResult();
}

但是当我尝试执行它时，我得到： "message": "[Semantical Error] line 0, col -1 near 'SELECT e.id,': Error: Cannot select entity through identification variables without choosing at least one root entity alias.", "class": "Doctrine''ORM''Query''QueryException",

在这里和这里寻找类似的问题，但这些都不适合我。我的实体如下所示：

<?php
namespace AppBundle'Entity;
use Doctrine'Common'Collections'ArrayCollection;
use Doctrine'ORM'Mapping as ORM;
use Symfony'Component'Validator'Constraints as Assert;
/** 
 * Place
 *
 * @ORM'Table(name="place")
 * @ORM'Entity(repositoryClass="AppBundle'Repository'PlaceRepository")
 */
class Place
{
/**
 * @var int
 *
 * @ORM'Column(name="id", type="integer")
 * @ORM'Id
 * @ORM'GeneratedValue(strategy="AUTO")
 */
private $id;
/**
 * @var string
 * @Assert'NotBlank()
 * @ORM'Column(name="title", type="string", length=255)
 */
private $title;
/**
 * @var string
 * @Assert'NotBlank()
 * @ORM'Column(name="address", type="string", length=255)
 */
private $address;
/**
 * @var float
 * @Assert'NotBlank()
 * @ORM'Column(name="lat", type="float")
 */
private $lat;
/**
 * @var float
 * @Assert'NotBlank()
 * @ORM'Column(name="lng", type="float")
 */
private $lng;
/**
 * @var string
 *
 * @ORM'Column(name="description", type="text", nullable=true)
 */
private $description;
/**
 * @var string
 *
 * @ORM'Column(name="fb_page", type="string", length=255, nullable=true)
 */
private $fbPage;
/**
 * @Assert'NotBlank()
 * @ORM'ManyToOne(targetEntity="City")
 * @ORM'JoinColumn(name="city_id", referencedColumnName="id")
 */
private $city;
/**
 * @Assert'NotBlank()
 * @ORM'ManyToOne(targetEntity="Category", inversedBy="places")
 * @ORM'JoinColumn(name="category_id", referencedColumnName="id")
 */
private $category;
/**
 * @var string
 *
 * @ORM'Column(name="site_url", type="string", length=255, nullable=true)
 */
private $siteUrl;
/**
 * @ORM'ManyToMany(targetEntity="WorkingTime", cascade={"persist"})
 * @ORM'JoinTable(name="places_workingtimes",
 *      joinColumns={@ORM'JoinColumn(name="place_id", referencedColumnName="id")},
 *      inverseJoinColumns={@ORM'JoinColumn(name="workingtime_id", referencedColumnName="id", unique=true)}
 *      )
 */
private $workingTimes;
/**
 * @var string
 * @ORM'Column(name="phone_no", type="string", length=255, nullable=true)
 *
 */
private $phoneNo;
/**
 * @ORM'OneToMany(targetEntity="Rating", mappedBy="place")
 */
private $ratings;

}`

namespace AppBundle'Entity;
use Doctrine'ORM'Mapping as ORM;
 /**
 * Rating
 *
 * @ORM'Table(name="rating")
 * @ORM'Entity(repositoryClass="AppBundle'Repository'RatingRepository")
 */
class Rating
{
/**
 * @var int
 *
 * @ORM'Column(name="id", type="integer")
 * @ORM'Id
 * @ORM'GeneratedValue(strategy="AUTO")
 */
private $id;
/**
 * @var int
 *
 * @ORM'Column(name="rating", type="smallint")
 */
private $rating;
/**
 * @ORM'ManyToOne(targetEntity="Place", inversedBy="ratings")
 * @ORM'JoinColumn(name="place_id", referencedColumnName="id")
 */
private $place;
/**
 * @ORM'ManyToOne(targetEntity="User")
 * @ORM'JoinColumn(name="user_id", referencedColumnName="id")
 */
private $user;

此错误仅在我尝试选择"w"时发生。那么，如何加入这个对象集合呢？