按数组元素分组的数组中匹配字符串的MongoDB计数

Question

我有一个MongoDB集合，存储调查的答案。答案通常是单选按钮，有“优秀”、“好”或“差”这样的回答。我试图生成一个查询，为每个问题返回给定响应的总数。响应当前存储在字符串数组中。数组中的位置0是问题1的答案，依此类推。

我目前有一个聚合查询，它以下列截断格式返回数据：

[{ 
    "name" : "Medical Visit Survey", 
    "question" : [
        "Ease of making an appointment?", 
        "About how long was your wait time before being seen by the provider?", 
        "Professionalism of person who took your call?"
    ], 
    "type" : [ "radiobutton", "radiobutton", "radiobutton" ], 
    "answers" : [ "Excellent",  "Less than 20 minutes", "Excellent" ]
},
{ 
    "name" : "Medical Visit Survey", 
    "question" : [
        "Ease of making an appointment?", 
        "About how long was your wait time before being seen by the provider?", 
        "Professionalism of person who took your call?"
    ], 
    "type" : [ "radiobutton",  "radiobutton", "radiobutton" ], 
    "answers" : ["Excellent",  "Less than 20 minutes",  "Very Good" ]
}]

生产产出的最佳方式如下所示：

[{
   "name" : "Medical Visit Survey",
   "question" : "Ease of making an appointment?",
   "type" : "radiobutton",
   "answers": { 
                 "Excellent": 2,
                 "Good": 3,
                 "Poor": 1
              }
  
},
{
   "name" : "Medical Visit Survey",
   "question" : "About how long was your wait time before being seen by the provider?",
   "type" : "radiobutton",
   "answers": { 
                 "Less than 20 minutes": 2,
                 "More than 20 minutes": 3,
                 "More than 60 minutes": 1
              }
  
}
]

我尝试了类似于以下几个方面的查询：

[
  {$unwind: "$answers" },
  { $group: { _id: "$answers", count: { $sum: 1 } } }
]

输出根据给定的答案对响应进行计数，但不考虑问题号(元素在数组中的位置)。

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如能提供任何协助，将不胜感激。

Answer 1

我不确定有什么最好的方法来做到这一点，但我建议一个聚合查询，

• $unwind解构question数组，并在每个问题元素中的index字段中包含数组索引。
• $arrayElemAt用于选择所提供的index字段的特定answer，对于type字段也一样
• $group by question和answer，选择所需字段并计数总计
• $group仅由question实现，并以键值格式构造answers数组。
• $arrayToObject将answers数组转换为对象

[
  {
    $unwind: {
      path: "$question",
      includeArrayIndex: "index"
    }
  },
  {
    $group: {
      _id: {
        question: "$question",
        answer: { $arrayElemAt: ["$answers", "$index"] }
      },
      name: { $first: "$name" },
      type: { $first: { $arrayElemAt: ["$type", "$index"] } },
      count: { $sum: 1 }
    }
  },
  {
    $group: {
      _id: "$_id.question",
      answers: {
        $push: { k: "$_id.answer", v: "$count" }
      },
      name: { $first: "$name" },
      type: { $first: "$type" }
    }
  },
  { $addFields: { answers: { $arrayToObject: "$answers" } } }
]

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