ruby-on-rails - Ruby .where 只计算一次重复的结果

Question

在我的 Rails 6/Grape API 应用程序中，我有一个模型 SurveyResult，我在其中存储用户提交的调查结果。

给定问题的调查结果可能很少(可以是多项选择题):

[31] pry(main)> SurveyResult.where(survey: survey, user: user)
 #<SurveyResult:0x00007f9283adca10
  id: 18,
  user_id: 1,
  survey_id: 1,
  cms_question_id: 5844869,
  cms_answer_id: 321,

 #<SurveyResult:0x00007f9283adc7e0
  id: 20,
  user_id: 1,
  survey_id: 1,
  cms_question_id: 5899779,
  cms_answer_id: 0987,

 #<SurveyResult:0x00007f9283adc920
  id: 21,
  user_id: 1,
  survey_id: 1,
  cms_question_id: 5899779,
  cms_answer_id: 12, 

例如，相同的 cms_question_id 有两个结果 - 5899779(如上)。现在，如果我想计算所有用户 SurveyResults，我将得到以下结果:

[31] pry(main)> SurveyResult.where(survey: survey, user: user).count
=> 3

如何修改此查询以仅计算具有相同 cms_question_id 的 SurveyResult 一次？上述示例的预期结果应为:

[31] pry(main)> SurveyResult.where(survey: survey, user: user).count
=> 2

Answer 1

查看 count文档将是:

SurveyResult.where(survey: survey, user: user).distinct.count(:cms_question_id)

count(column_name = nil)

Count the records.

Person.count
# => the total count of all people

Person.count(:age)
# => returns the total count of all people whose age is present in database

Person.count(:all)
# => performs a COUNT(*) (:all is an alias for '*')

Person.distinct.count(:age)
# => counts the number of different age values