symfony - 语法错误: line 0, col 81 : Error: Expected Literal,得到了 'NULL'

Question

尝试通过查询生成器执行查询时收到错误[Syntax Error] line 0, col 81: Error: Expected Literal, got 'NULL'

        $qb = $this->createQueryBuilder('r')
            ->select('r')
            ->where('r.query = :query')
            ->setParameter('query', $query)   
            ->andWhere('r.lang = NULL')
        ;

        return $qb->getQuery()->getOneOrNullResult();

r.lang字段定义为:

/**
 * @var integer
 *
 * @ORM\ManyToOne(targetEntity="\BW\LocalizationBundle\Entity\Lang")
 * @ORM\JoinColumn(name="lang_id", referencedColumnName="id")
 */
private $lang;

帮助解决错误，请

Answer 1

当您检查NULL值时，表达式应为

->andWhere('r.lang IS NULL')