加入時的學說查詢構建器錯誤

Question

如何使用學說查詢構建器編寫以下內容？

SELECT 
    registry.id , 
    registry.couple_id, 
    registry.gift_id, 
    Sum(purchase.amount) as totalContribution, 
    gift.title, 
    gift.price 
FROM 
    gift, 
    registry 
LEFT JOIN 
    purchase ON purchase.registry_id = registry.id 
WHERE 
    registry.gift_id = gift.id 
    AND registry.couple_id = 1 
GROUP BY 
    registry.couple_id, 
    registry.gift_id 

我想：

$qb = $this->createQueryBuilder('g') //gift 
    ->from('\BBB\GiftBundle\Entity\Registry', 'reg') 
    ->select('g.id , g.title, g.description, g.price, g.imageMedium') 
    ->addSelect('SUM(p.amount) as totalContribute') 
    ->leftJoin('\BBB\GiftBundle\Entity\Purchase', 'p', 'ON','reg.id = p.registry') 
    ->where('reg.gift = g.id') 
    ->AndWhere('reg.couple = :coupleID') 
    ->orderBy('reg.id','DESC') 
    ->groupBy('reg.couple') 
    ->groupBy('reg.gift') 
    ->setParameter('coupleID', $coupleID); 

但它給了我以下錯誤：

[Semantical Error] line 0, col 178 near 'p ON reg.id =': Error: Identification Variable BBB\GiftBundle\Entity\Purchase used in join path expression but was not defined before.

Answer 1

DQL只能加入與當前實體表（即是在此DQL Registry）。你的Registry實體將需要聲明OneToMany關係。

假設這種關係被稱爲purchases你會加入像這樣：

->leftJoin('reg.purchases', 'p')