综合平均值

Question

我希望在 MongoDB 聚合中找到的平均值得出一个综合值

 [
      {
        "_id": "581c3d9c55421c16ecaf0b26",
        "uDept": "CoE Design & Research",
        "uName": "Saurabh Raman",
        "rateVal": 3,
        "timeStamp": "11/4/2016 13:17",
        "__v": 0
      },
      {
        "_id": "581c437ea3d9f6087ce3b21e",
        "uDept": "CoE Design & Research",
        "uName": "Sachin P Singh",
        "rateVal": 4,
        "timeStamp": "11/4/2016 13:42",
        "__v": 0
      },
      {
        "_id": "581c6d74a3d9f6087ce3b21f",
        "uDept": "Training",
        "uName": "Rahul Shakya",
        "rateVal": 4,
        "timeStamp": "11/4/2016 16:35",
        "__v": 0
      }
    ]

我运行以获取“rateVal”平均值的查询

db.calcR.aggregate([
    {
            $group: {
                _id: null,  

                avg: {$avg: '$rateVal'},

            }
    }

输出是{ avg: 3.6666 }但理想情况下我希望它显示为 4

[
  {
    "_id": null,
    "avg": 3.6666666666666665,

  }
]

Answer 1

要舍入 mongoDb 中的值，您可以使用$ceil或$floor

db.calcR.aggregate([
    {
            $group: {
                _id: null,  

                avg: {$avg: '$rateVal'},

            },
           $project:{
               _id: '$_id' ,
               roundedAvg : { $ceil: '$avg' }
           }
    }]

输出看起来像

[
  {
    "_id": null,
    "roundedAvg": 4,

  }
]