Rails 3:Arel 不存在? [英] Rails 3: Arel for NOT EXISTS?

问题描述

您如何在 Arel 中编写 NOT EXISTS ?我无法将此查询转换为 Arel:

How do you write a NOT EXISTS in Arel? I'm having trouble translating this query into Arel:

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
   )
 )

推荐答案

这就是答案，名字很奇怪，因为我不知道如何为我不知道的域命名.

Here is the answer, with strange names because I don't know how to give names for a domain that is for me unknown.

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)

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