将Postgres查询转换为Rails ActiveRecord吗？

Question

是否可以用Rail的ActiveRecord格式编写以下查询？ 我尝试了十亿种不同的Arel方法，但无法获得相同的结果。

SELECT topic_id, count(*) as total
FROM questions_topics
WHERE question_id IN (
  SELECT id
  FROM questions
  WHERE user_id = 1000
  UNION ALL
  SELECT questions.id
  FROM questions JOIN answers ON (questions.id = answers.question_id)
  WHERE answers.user_id = 1000
)
GROUP BY topic_id
ORDER BY total DESC;

Answer 1

好吧，这应该工作。 并非完全相同，但应给出相同的结果。

QuestionTopic.where(
  "question_id IN (?) OR question_id IN (?)",
  Question.where(user_id: 1000).select(:id),
  Answer.where(user_id: 1000).select(:question_id)
).group('topic_id')
 .order('total desc')
 .select('topic_id, count(*) as total')