Rails 5复杂连接查询

Question

我有一个有效的联接查询：

目标是通过campaign_addings检索与id（Array）中ID不相关的候选人

Candidate.joins("LEFT OUTER JOIN campaign_addings ON campaign_addings.candidate_id = candidates.id AND campaign_addings.campaign_id IN (#{id.join(',')})").where('campaign_addings.candidate_id IS NULL')

但是很好..这个查询非常难看，我想用纯ActiveRecord DSL重新创建这种行为而没有SQL，我现在有这个：

Candidate.left_outer_joins(:campaign_addings).where(campaign_addings: { campaign_id: id, candidate_id: nil })

好的查询生成：

SELECT COUNT(*) FROM "candidates" LEFT OUTER JOIN campaign_addings ON campaign_addings.candidate_id = candidates.id AND campaign_addings.campaign_id IN (4) WHERE (campaign_addings.candidate_id IS NULL)

糟糕的一个：

SELECT COUNT(DISTINCT "candidates"."id") FROM "candidates" LEFT OUTER JOIN "campaign_addings" ON "campaign_addings"."candidate_id" = "candidates"."id" WHERE "campaign_addings"."campaign_id" = 4 AND "campaign_addings"."candidate_id" IS NULL

你可以看到它非常接近，但我认为我遗漏了一些东西，无法找到加入第一个查询的方法。

编辑：

另外，还有一个SQL注入漏洞