我想计算 nodejs mongodb 列中的三个字段，需要按月分组

Posted 2023-03-08

【中文标题】我想计算 nodejs mongodb 列中的三个字段，需要按月分组

【英文标题】：I want to count three fields in a nodejs mongodb column and need to group it by month

【发布时间】：2021-06-22 13:07:21

【问题描述】：

我想统计每个月green,red,amber 的数量（即：按月分组），如下例所示：

_id:2,Green:20,Red:12,Amber:23

说_id代表月份（2:Feb）

注意：- 我正在从 mongodb 检索数据，并且日期列是 ISO 日期类型格式

谁能帮帮我？

【问题讨论】：

如果您的日期实际上不是一个字符串，正如您最初的问题所暗示的那样，您最好在节点中完成整个操作。

【参考方案1】：

演示 - https://mongoplayground.net/p/0N7b2uNZJNL

db.collection.aggregate(
  "$project": 
    color: 1,
    month: 
      "$substr": [ "$date", 0,  "$indexOfCP": [ "$date", "/" ]  // extract month from date string
      ]
    
  
,

  "$group": 
    "_id":   month: "$month", color: "$color" ,
    "count":  "$sum": 1 
  
,

  "$project": 
    month: "$_id.month",
    details: [  color: "$_id.color", count: "$count"  ] // add color count to the array
  
,

  $project: 
    _id: 0,
    month: 1,
    color: 
      $arrayToObject:  // get object from array like green: 1
        $map: 
          input: "$details", as: "pair", in: [ "$$pair.color",  "$$pair.count" ]
        
      
    
  
,

  "$group": 
    "_id": "$month",
    "color":  "$mergeObjects": "$color"  // merge all the colors
  
,

  $replaceWith: 
    $mergeObjects: [   _id: "$_id"  , "$color" ] // bring color out of the object
  
)

$substr

$indexOfCP

$arrayToObject

$mergeObjects

$replaceWith

【讨论】：

谢谢，它运行良好，而且我只想从中检索最近三个月

@hariram 使用 $sort 和 $limit

【参考方案2】：

试试这个查询：

db.colors.aggregate([
    
        $group: 
            _id: 
                month:  $month: "$Date" ,
                color: "$Rag"
            ,
            count:  $sum: 1 
        
    ,
    
        $group: 
            _id: "$_id.month",
            array: 
                $push: 
                    k: "$_id.color",
                    v: "$count"
                
            
        
    ,
    
        $replaceRoot: 
            newRoot: 
                $arrayToObject: 
                    $concatArrays: [[ k: "_id", v: "$_id" ], "$array"]
                
            
        
    
]);

问题中附加的测试数据的输出：

    "_id" : 3,
    "Red" : 1,
    "Amber" : 14,
    "Green" : 7

colors 集合中的数据：

[
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Green"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Red"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  ,
  
    "_id": ObjectId("..."),
    "Date": ISODate("2021-03-16T00:00:00.000+05:30"),
    "Rag": "Amber"
  
]