Doctrine \ ORM \ Query \ QueryException [语义错误] ...：错误：未定义类'NULL'。 在QueryBuilder中使用NULL时

$result = $this->er->createQueryBuilder("r")
            ->select("COUNT(r.customer IS NOT NULL) as customers")
            ->getQuery()
            ->getResult(AbstractQuery::HYDRATE_ARRAY);

I'm trying to run this query using Doctrine Query Builder but it returns this error: Doctrine\ORM\Query\QueryException [Semantical Error] ...: Error: Class 'NULL' is not defined. when using NULL What am I doing wrong? How can I implement IS NOT NULL into my query?

EDIT

Also, please consider this:

$result = $this->er->createQueryBuilder("r")
                ->select(
                         "COUNT(r.customer) as customers_total", 
                         "COUNT(r.customer IS NOT NULL) as customers_set", 
                         "COUNT(r.customer IS NULL) as customers_unset"
                )
                ->getQuery()
                ->getResult(AbstractQuery::HYDRATE_ARRAY);

Therefore, adding ->where("r.customer IS NOT NULL") would't work much here. My first question wasn't defined precisely. I'm sorry about that.

This solution works for me:

$result = $er
            ->createQueryBuilder("r")
            ->select("COUNT(r.customer) as customers_total")
            ->addSelect("SUM(CASE WHEN r.customer IS NOT NULL THEN 1 ELSE 0 END) as customers_set")
            ->addSelect("SUM(CASE WHEN r.customer IS NULL THEN 1 ELSE 0 END) as customers_unset")
            ->getQuery()
            ->getResult(AbstractQuery::HYDRATE_ARRAY);

Try this

$result = $this->er->createQueryBuilder("r")
            ->select("COUNT(*) as customers")
            ->where("r.customer IS NOT NULL")
            ->getQuery()
            ->getResult(AbstractQuery::HYDRATE_ARRAY);

EDIT :

If you want a more complex request

    $this->er->createQueryBuilder("r")
                    ->select("COUNT(r.customer) as customers_total,
COUNT(case when r.customer IS NOT NULL then 1 end) as customers_set,
COUNT(case when r.customer IS NULL then 1 end) as customers_unset
")
                    ->getQuery()
                    ->getResult(AbstractQuery::HYDRATE_ARRAY);