Question

以下模型星座：

class Attempt < ApplicationRecord
  belongs_to :user
  belongs_to :answer
  belongs_to :question
end

class Answer < ApplicationRecord
  belongs_to :question
end

class Question < ApplicationRecord
  has_many :answers
  has_many :attempts
end

一个问题有几个答案，其中一个被标记为正确（列correct）。用户试图猜出问题的正确答案。

挑战：我想知道每个问题的用户，尝试成功的次数（选择的正确答案）以及失败的次数，而不会针对数据库触发多次/多次查询。

让我最接近满意答案的是Question.joins(attempts: [:answer]).group('(attempts.question_id, answers.correct)').count（到目前为止忽略那里的用户）。结果SQL：

SELECT COUNT(*) AS count_all, (attempts.question_id, answers.correct) AS attempts_question_id_answers_correct FROM "questions" INNER JOIN "attempts" ON "attempts"."question_id" = "questions"."id" INNER JOIN "answers" ON "answers"."id" = "attempts"."answer_id" GROUP BY (attempts.question_id, answers.correct)

这些值是正确的，但结果看起来很奇怪，这些＆＃34;（1，f）等。＆＃34;键：

{"(1,f)"=>4, "(3,t)"=>2, "(2,t)"=>4, "(2,f)"=>11, "(3,f)"=>6, "(1,t)"=>4}

我很感激任何帮助，尤其是结果集:)。非常感谢提前！

Answer 1

你试过这个：

Question.joins(attempts: [:answer]).select("attempts.question_id as question_id, answers.correct as correct_answer").group('(attempts.question_id, answers.correct)').count

Rails计数并按两个属性分组

1 个答案: