Day 10: DB へ情報入力、ページに出力

 / #cebu #rails #mysql

from Qiita: マスターデータ（DBへ情報入力、ページに出力

Environment

仮想環境 OS: Ubuntu 18.04 Ruby：2.51 Rails:5.2.2

流れ

  1. 中間テーブルにデータ入力
  2. 性別の 0 or 1 の表記を、male or female に変更
  3. Student の show ページに、生徒ごとの試験結果など、データを出力

実段階

生徒データと関連付けするときは

student1 = Student.first
student1.clubs << Club.first
student1.save

データ入力

id1 から id100 までの生徒に、0 から 4 個の部活(選択肢は 13 部)に入ってもらう。

(1..100).each do |i|
  student = Student.find(i)
  1.upto(rand(0..4)) do
    student.clubs << Club.find(rand(1..13))
    student.save
  end
end

生徒の試験結果情報 id100 までの生徒に、9 科目の試験を受けてもらう。

(1..100).each do |i|
  student = Student.find(i)
  1.upto(9) do |num|
    sub = Subject.find(num)
    exam_res = ExamResult.new
    exam_res.name = "試験#{num}"
    exam_res.score = rand(1..sub.max_score)
    exam_res.subject = sub
    student.exam_results << exam_res
    student.save
  end
end

Studentsのindexページの表記を変更

enum gender: { male: 0 ,female: 1}
enum age: {"teen": 0, "twenty": 1}
<div class="field">
    <%= form.label :gender %>
    <%= form.radio_button :gender, 'male' %>男性
    <%= form.radio_button :gender, 'female' %>女性
</div>
<div class="field">
    <%= form.label :age %>
    <%= form.radio_button :age, '20代' %>20代
    <%= form.radio_button :age, '30代' %>30代
</div>

出力を考える

  • 学生ごとの show ページで表示したいもの
    • 生徒のデータ(name, mail, gender, age, opinion)
    • 生徒の教科ごとの試験結果点数
    • 性と全体の試験結果の平均点、最大点、最小点

MySQL上の出力

SELECT
    subjects.name,
    CAST(AVG(exam_results.score) as unsigned) as avg_score,
    MAX(exam_results.score) as max_score,
    MIN(exam_results.score) as min_score
FROM
    students
INNER JOIN exam_results
    ON students.id = exam_results.student_id
INNER JOIN subjects
    ON exam_results.subject_id = subjects.id
GROUP BY subjects.id, subjects.name


-- =>
-- +--------+--------------+-----------+-------+-------+
-- | name   | name         | name      | score | ratio |
-- +--------+--------------+-----------+-------+-------+
-- | taro-1 | 一次試験     | 数学      |   181 |    91 |
-- | taro-1 | 試験1        | 数学      |    61 |    31 |
-- | taro-1 | 一次試験     | 国語      |   146 |    73 |
-- ...

ページ上の出力

students_controllerのshowアクション編集
def show
    @students = 
      Student.joins(:subjects)
              .select('students.name, students.email, students.age, students.gender, students.opinion, subjects.id as subject_id')
              .select('exam_results.name as exam_result_name, subjects.name as subject_name, exam_results.score')
              .select('CAST((exam_results.score / subjects.max_score) * 100 as unsigned) as ratio')
              .where(id: params[:id])


    avg_result = 
      Student.joins(:subjects)
              .select('subjects.id as subject_id')
              .select('CAST(AVG(exam_results.score) as unsigned) as avg_score')
              .select('MAX(exam_results.score) as max_score')
              .select('MIN(exam_results.score) as min_score')
              .group('subjects.id')
              .order('subjects.id')


    @score_hash = {}


    avg_result.each do |avg_res|
      h = Hash.new
      h[:avg_score] = avg_res.avg_score
      h[:max_score] = avg_res.max_score
      h[:min_score] = avg_res.min_score                                                                                                                                     
      @score_hash[avg_res.subject_id] = h
    end
  end
showページのviewを編集
<table border="1">
  <tr>
    <th>科目名</th>
    <th>点数</th>
    <th>平均</th>
    <th>最高</th>
    <th>最小</th>
  </tr>
  <% @students.each do |student| %>
    <tr>
      <td><%= student.subject_name %></td>
      <td><%= student.score %></td>
      <td><%= @score_hash[student.subject_id][:avg_score] %></td>
      <td><%= @score_hash[student.subject_id][:max_score] %></td>
      <td><%= @score_hash[student.subject_id][:min_score] %></td>
    </tr>              
  <% end %>
</table>