MongoDB聚合查询求助：如何用$match与$group生成目标数据格式

原始数据（Answer集合） #

[ {
    _id: new ObjectId("6357b4237cf79bba3e66c096"),
    userId: new ObjectId("635762fe85b94eac7466d965"),
    formId: new ObjectId("6357921d49de88bb7fffcfe4"),
    title: 'Quality',
    username: 'Jansenstan24@gmail.coms',
    date: '2022-10-25',
    answer: {
      '6357921d49de88bb7fffcfe8': 'john@nabatisnack.com',
      Text: 'john@nabatisnack.com',
      '6357b331235053a9d4e8d037': 'john@dose.com',
      Email: 'john@dose.com',
      '6357b335235053a9d4e8d03a': 'Maja',
      Plant: 'Maja'
    },
    createdAt: 1666692131,
    updatedAt: 1666692131,
    __v: 0
  },
  {
    _id: new ObjectId("6357b54922866fae378af370"),
    userId: new ObjectId("635762fe85b94eac7466d965"),
    formId: new ObjectId("6357921d49de88bb7fffcfe4"),
    title: 'Quality',
    username: 'Jansenstan24@gmail.coms',
    date: '2022-10-25',
    answer: {
      '6357921d49de88bb7fffcfe8': 'john@dose.com',
      Text: 'john@dose.com',
      '6357b331235053a9d4e8d037': 'john@nabatisnack.com',
      Email: 'john@nabatisnack.com',
      '6357b335235053a9d4e8d03a': 'Cica',
      Plant: 'Cica'
    },
    createdAt: 1666692425,
    updatedAt: 1666692425,
    __v: 0
  },
  {
    _id: new ObjectId("6357b6a2a13ab3c4a462be8f"),
    userId: new ObjectId("635647c1e24d0a4482e3c0a9"),
    formId: new ObjectId("6357921d49de88bb7fffcfe4"),
    title: 'Quality',
    username: 'adam@wegodev.com',
    date: '2022-10-25',
    answer: {
      '6357921d49de88bb7fffcfe8': '12',
      Text: '12',
      '6357b331235053a9d4e8d037': 'john@dose.coms',
      Email: 'john@dose.coms',
      '6357b335235053a9d4e8d03a': 'Ranca',
      Plant: 'Ranca'
    },
    createdAt: 1666692770,
    updatedAt: 1666692770,
    __v: 0
  }]

当前错误的聚合尝试 #

forms = await Answer.aggregate([
          {
            $match: { title: "Quality" },
          },
          { $group: { title: "Quality"} },

        ]);

期望的输出格式 #

{
    formId: new ObjectId("6357921d49de88bb7fffcfe4"),
    title: 'Quality',
    username: ['Jansenstan24@gmail.coms','adam@wegodev.com'],
    date: ['2022-10-25'],
    answer: [{
      '6357921d49de88bb7fffcfe8': 'john@nabatisnack.com',
      Text: 'john@nabatisnack.com',
      '6357b331235053a9d4e8d037': 'john@dose.com',
      Email: 'john@dose.com',
      '6357b335235053a9d4e8d03a': 'Maja',
      Plant: 'Maja'
    },{
      '6357921d49de88bb7fffcfe8': 'john@dose.com',
      Text: 'john@dose.com',
      '6357b331235053a9d4e8d037': 'john@nabatisnack.com',
      Email: 'john@nabatisnack.com',
      '6357b335235053a9d4e8d03a': 'Cica',
      Plant: 'Cica'
    },{
      '6357921d49de88bb7fffcfe8': '12',
      Text: '12',
      '6357b331235053a9d4e8d037': 'john@dose.coms',
      Email: 'john@dose.coms',
      '6357b335235053a9d4e8d03a': 'Ranca',
      Plant: 'Ranca'
    }],
  }

正确的聚合查询写法 #

forms = await Answer.aggregate([
  // 筛选目标表单数据
  { $match: { title: "Quality" } },
  // 按表单分组聚合字段
  {
    $group: {
      _id: { formId: "$formId", title: "$title" },
      username: { $addToSet: "$username" },
      date: { $addToSet: "$date" },
      answer: { $push: "$answer" }
    }
  },
  // 调整输出结构，匹配期望格式
  {
    $project: {
      _id: 0,
      formId: "$_id.formId",
      title: "$_id.title",
      username: 1,
      date: 1,
      answer: 1
    }
  }
]);

关键步骤说明 #

• $match：精准过滤title为Quality的文档，减少聚合计算的数据量。
• $group：
  • 以formId和title作为分组依据，确保同一表单的数据被聚合到一起。
  • $addToSet：收集去重的username和date，避免重复值。
  • $push：将每个文档的answer对象完整添加到数组中，保留所有提交的答案。
• $project：重新组织输出结构，将_id中的字段提取为顶层字段，并移除默认的_id字段，完全匹配期望的格式。

内容的提问来源于stack exchange，提问作者JS24