如何在rails中的一行中显示来自多个表的数据

Question

I have two tables - Reports and Subjects. How can query and display data from two tables in one line in Rails?

Here are the relationships:

class Subject < ActiveRecord::Base
 has_many :term_reports
end

class TermReport < ActiveRecord::Base
 belongs_to :subject
end

Here are the schemas:

create_table "subjects", force: true do |t|
 t.string  "name"
 t.integer "user_id"
 t.date    "createdate"
end

create_table "term_reports", force: true do |t|
 t.string  "student_studentid"
 t.integer "subject_id"
 t.integer "score"
 t.integer "position"
 t.integer "term"
 t.integer "year"
 t.integer "user_id"
 t.date    "ceatedate"
 t.string  "remark"
 t.string  "form_class"
end

Now I want the data is this format:

Sujectname score position etc..

Note that the subject name is stored in Sujects table. The bolow code is producing data from one table only:

@student_subject = TermReport.includes(:subject).all
@student_subject = TermReport.joins(:subject).all

However, this sql is working very well in Workbench but displaying data from one table if I use find_by_sql. Help

select * from term_reports t, subjects s
where t.subject_id = s.id

Answer 1

This should work just fine you can try it on your console:

TermReport.includes(:subject).all.each do |term|
  puts "#{term.subject.name} #{term.score} #{term.position}"
end

And TermReport.all is enough I don't think you need includes(:subject).

Answer 2

Thanks Smek. Here is my controller action:

  def search_student_results
   @student_subject = TermReport.where("student_studentid =? and year =? and term =? and form_class =?",
                          params[:studentid], params[:year], params[:term], params[:formclass])
   respond_to do |format|
   format.js  {render json: @student_subject}
   end
end

And here is my ajax call:

$(function() {
$('#subject_search_btn').click(function() {
    var student_id = $('#search').val();
    var year = $('#year').val();
    var term = $('#term').val();
    var classs = $('#formclass').val();

    $.ajax({
        "url": "/search_student_results",
        "data": {"studentid":student_id, "year":year, "term":term, "formclass":classs},
        "type": "get",
        "dataType": "json",
        "success": function(data) {
            var trHTML = '';
            $.each(data, function (i, item) {
                trHTML += '<tr>' +
                    '<td>' + item.subject_id + '</td>' +
                    '<td>' + item.score + '</td>' +
                    '<td>' + item.position + '</td>' +
                    '<td>' + item.remark + '</td>' +
                    '</tr>';
            });
            $('#subject_tbody').append(trHTML);
        },
        "error": function() {
            alert('Student not found');
        }
    });
});
});

How can I replace item.subject_id with item.subject.name? Thanks

Answer 3

So to answer your last question.

You can change:

format.js  {render json: @student_subject}

With:

format.json do
    render json: @student_subject.as_json(include: { subject: { only: :name } })
end