MySQL，Highcharts：“操作数应该包含1列：”错误（后续） [英] MySQL, Highcharts: “operand should contain 1 column(s):” error (follow up)

问题描述

控制器

我试图通过收集ID数组来呈现数据到样条图上。 pre> def student_feedback
difficulty_ids = current_user.school_user.homework_students.pluck（：difficulty）
@homeworks = HomeworkStudent.where（homework_id =（？），difficulty_ids ）.first
end


我的目标表称为homework_students：

  create_tablehomework_students，force：：cascade do | t | 
 t.integerschool_user_id，限制：4，null：false 
 t.integerhomework_id，限制：4，null：false 
 t.datetimecompleted_on
 t.datetimecreated_at，null：false 
 t.datetimeupdated_at，null：false 
 t.booleancompleted，limit：1 
 t.integerdifficulty，limit ：4 
 t.integerinterest，limit：4 
 end 
  

每个学生都有许多不同的家庭作业，他们可以在每个难度栏中分配一个难度值。我正在为每个学生绘制这些数据。

因此，在上面的控制器动作中，我正在为当前用户在数组中关联的每项作业摘取难度数字（1 - 5）。

在我的图表中：

  ... 
} 
}，
系列：[{
名称：'难度'，
数据：[<％= @ homeworks.to_json％>] 
}] 
 }）; 
  

我尝试将操作更改为此：

  def student_feedback 
 difficulty_ids = current_user.school_user.homework_students.pluck（：difficulty）
 @homeworks = HomeworkStudent.where（[homework_id =？，difficulty_ids]） .first 
 end 
  

我一直收到这个错误：

  Mysql2 :: Error：操作数应该包含1列：SELECT`homework_students`。* FROM`homework_students` WHERE（homework_id =（4,2,1 ，2,3））ORDER BY`homework_students`.`id` ASC LIMIT 1 
  

收集的是正确的。虽然它说homework_id = 4,2 ..（这是不正确的，这些是难度值）。我怀疑这只是一个语法错误。我玩了一下。可以提供更多的代码，如果需要的话。

我理解这个问题，但它只是语法...

很多感谢任何帮助。谢谢

更新：一些进展......

 }，
系列：[{
 pointInterval：<％= 1.day * 1000％> ;, 
 pointStart：<％= 3.weeks.ago.at_midnight.to_i * 1000％> ，
名称：'难度'，
数据：<％= Homework.get_difficulty.to_json％> 
}，
  

在我的homework.rb模型中：

  def self.get_difficulty 
 HomeworkStudent.pluck（：difficulty）
 end 
  

这产生：

但是，这显然是所有记录，而我只希望当前用户显示，并且我不知道如何正确设置日期（updated_at属性）。

解决方案

我认为您的SQL错误，请尝试homework_id in（？） c>> homework_id =（？）来选择具有多个值的行。

您的代码应该是：

  def student_feedback 
 difficulty_ids = current_user.school_user.homework_students.pluck（：难度）
 @homeworks = HomeworkStudent.where（[homework_id in（？），difficulty_ids]）。first 
 end 
  

I am trying to render data on to a spline chart by collecting an array of id's:

Controller

def student_feedback
        difficulty_ids = current_user.school_user.homework_students.pluck(:difficulty)
        @homeworks = HomeworkStudent.where("homework_id = (?)", difficulty_ids).first
    end

The table I am targeting is called homework_students:

create_table "homework_students", force: :cascade do |t|
    t.integer  "school_user_id", limit: 4, null: false
    t.integer  "homework_id",    limit: 4, null: false
    t.datetime "completed_on"
    t.datetime "created_at",               null: false
    t.datetime "updated_at",               null: false
    t.boolean  "completed",      limit: 1
    t.integer  "difficulty",     limit: 4
    t.integer  "interest",       limit: 4
  end

Each student has many different homeworks and they can assign a difficulty value in the difficulty column for each. I am looking to graph this data for each student.

So in the above controller action I am plucking difficulty figures (1 - 5) for each piece of homework the current user is associated with in an array.

In my chart:

...
       }
        },
        series: [{
            name: 'Difficulty',
            data: [<%= @homeworks.to_json %>]
        }]
    });

I tried changing action to this:

  def student_feedback
            difficulty_ids = current_user.school_user.homework_students.pluck(:difficulty)
            @homeworks = HomeworkStudent.where(["homework_id = ?", difficulty_ids]).first
        end

I keep getting this error:

Mysql2::Error: Operand should contain 1 column(s): SELECT `homework_students`.* FROM `homework_students` WHERE (homework_id = (4,2,1,2,3)) ORDER BY `homework_students`.`id` ASC LIMIT 1

The data being collected is correct. Though it says "homework_id = 4,2.." (this is not correct, those are the difficulty values). I suspect this is just a syntax error. I have toyed around a little bit. Can provide more code if needed.

I understand the problem but it's just the syntax...

Much appreciate any help. Thanks

UPDATE: Some progress...

      },
series: [{
    pointInterval: <%= 1.day * 1000 %>,
    pointStart: <%= 3.weeks.ago.at_midnight.to_i * 1000 %>,
    name: 'Difficulty',
    data: <%= Homework.get_difficulty.to_json %>
     },

In my homework.rb model:

def self.get_difficulty
      HomeworkStudent.pluck(:difficulty)
    end

This produces:

But this is obviously for all records whereas I only want current user's to show and I don't know how to get the dates set up properly (updated_at attribute).

解决方案

I think your SQL is wrong, try "homework_id in (?)" instead of homework_id = (?), to select rows with multiple values.

Your code should be:

def student_feedback
    difficulty_ids = current_user.school_user.homework_students.pluck(:difficulty)
    @homeworks = HomeworkStudent.where(["homework_id in (?)", difficulty_ids]).first
end

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