Question

我有一个DB，可以存储学生对测验问题的答案。这些与学生学习成果有关，我想通过下面描述的一系列关系进行审查。我正在尝试计算正确回答了多少问题以及每个学生学习结果错误地回答了多少问题，但我一直收到错误。提前感谢您提供的任何帮助。

一般映射是

“答案”回答了一个问题，该问题测试了涵盖许多人的“KnowledgeTopic”（“KtCoveredBySLO”）“StudentLearningOutcome”

我的模型具有以下关系：

class Answer < ActiveRecord::Base
  belongs_to :KnowledgeTopic
end

class KnowledgeTopic < ActiveRecord::Base
  has_many :answers
  has_many :kt_covered_by_slos 
  has_many :student_learning_outcomes, through: :kt_covered_by_slos
end

class KtCoveredBySlo < ActiveRecord::Base
  belongs_to :StudentLearningOutcome
  belongs_to :KnowledgeTopic
end

class StudentLearningOutcome < ActiveRecord::Base
  has_many :kt_covered_by_slos 
  has_many :knowledge_topics, through: :kt_covered_by_slos
end

我试图运行的查询是：

@answers = Answer.joins(:KnowledgeTopic => {:kt_covered_by_slos => :StudentLearningOutcome})

.select( 'student_learning_outcomes.id As student_learning_outcomes_id', 
                 :is_correct, "count(answers.id) AS total_answers")

 .group('student_learning_outcomes.id', :is_correct)

我收到的错误是：

SQLite3 :: SQLException：没有这样的列：   kt_covered_by_slos.knowledge_topic_id：SELECT   student_learning_outcomes.id作为student_learning_outcomes_id，   ＆＃34;答案＆＃34;。＆＃34; is_correct＆＃34;，count（answers.id）AS total_answers FROM   ＆＃34;答案＆＃34; INNER JOIN＆＃34; knowledge_topics＆＃34; ON＆＃34; knowledge_topics＆＃34;。＆＃34; id＆＃34;   =＆＃34;答案＆＃34;。＆＃34; KnowledgeTopic_id＆＃34; INNER JOIN＆＃34; kt_covered_by_slos＆＃34; ON＆＃34; kt_covered_by_slos＆＃34;。＆＃34; knowledge_topic_id＆＃34; =＆＃34; knowledge_topics＆＃34;。＆＃34; id＆＃34;
  INNER JOIN＆＃34; student_learning_outcomes＆＃34;上   ＆＃34; student_learning_outcomes＆＃34;＆＃34; ID＆＃34; =   ＆＃34; kt_covered_by_slos＆＃34;＆＃34; StudentLearningOutcome_id＆＃34;通过...分组   student_learning_outcomes.id，is_correct

迁移

class CreateKtCoveredBySlos < ActiveRecord::Migration
  def change
    create_table :kt_covered_by_slos do |t|
      t.references :StudentLearningOutcome, index: true
      t.references :KnowledgeTopic, index: true

      t.timestamps
    end
  end
end

class CreateAnswers < ActiveRecord::Migration
  def change
    create_table :answers do |t|
      t.references :Question, index: true
      t.references :Section, index: true
      t.references :Student, index: true
      t.references :KnowledgeTopic, index: true
      t.boolean :is_correct
      t.string :answer_text
      t.references :Enroll, index: true

      t.timestamps
    end
  end
end

class CreateKnowledgeTopics < ActiveRecord::Migration
  def change
    create_table :knowledge_topics do |t|
      t.string :knowledge_area
      t.string :knowledge_unit
      t.string :knowledge_topic
      t.integer :year_added
      t.boolean :active
      t.integer :correct_answers
      t.integer :incorrect_answers
      t.integer :temp_correct_answer
      t.integer :temp_incorrect_answer
      t.timestamps
    end
  end
end

class CreateStudentLearningOutcomes < ActiveRecord::Migration
  def change
    create_table :student_learning_outcomes do |t|
      t.string :accredidation_body
      t.string :title
      t.string :description
      t.integer :year_added
      t.boolean :active
      t.integer :correct_answers
      t.integer :incorrect_answers
      t.integer :temp_correct_answer
      t.integer :temp_incorrect_answer
      t.timestamps
    end
  end
end

Answer 1

谢谢大家。使用Ave的解释，我更改了引用名称，然后相应地更新了其他所有内容。之后我能够用

运行查询

@answers = Answer.joins(knowledge_topic: :student_learning_outcomes)
.select( 'student_learning_outcomes.id As student_learning_outcomes_id', :is_correct,   
    "count(answers.id) AS total_answers")
.group('student_learning_outcomes.id', :is_correct)

Rails嵌套连接与has_many通关系

1 个答案: