Rails 3：Arel如何处理NOT EXISTS？

Question

如何在Arel中编写NOT EXISTS？我在将此查询翻译为Arel时遇到了麻烦：

SELECT * FROM deals 
WHERE NOT EXISTS (
   SELECT 1 FROM reward_deals 
   WHERE reward_deals.deal_id = deal.id 
   AND NOT (
      reward_deals.awarding_type = 'deal' 
      AND reward_deals.deal_id = reward_deals.awarding_id
   )
 )

- neezer

Answer 1

这是答案，名称很奇怪，因为我不知道如何为我未知的域名命名。

deals = Deal.arel_table
reward_deals = RewardDeal.arel_table
awarding_condition= reward_deals[:awarding_type].eq('deal')\
                                .and(reward_deals[:deal_id]\
                                       .eq(reward_deals[:awarding_id]))

reward_deals_condition= reward_deals[:deal_id].eq(deals[:id])\
                              .and(awarding_condition.not)
Deal.where(RewardDeal.where(reward_deals_condition).exists.not)

- Pedro Rolo

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然而，我的答案回答了你的问题，我的推测也是正确的。为什么你没有将我的答案标记为正确呢？！ - Pedro Rolo

必须自己尝试一下才能确定这是正确的答案。看起来这个方法很有效。谢谢！ - neezer