需要从mongodb中的数组对象值求和 [英] Need to sum from array object value in mongodb

问题描述

如果该值存在，我正在尝试计算总值.但是查询无法100％工作.所以有人可以帮助我解决这个问题.这是我的样本文件.我附上了两个文件.请这些文件和找出最佳解决方案 文件:1

I am trying to calculate total value if that value exits. But query is not working 100%. So can somebody help me to solve this problem. Here my sample document. I have attached two documents. Please these documents & find out best solution Document : 1

{
    "_id" : 1"),
    "message_count" : 4,
    "messages" : {
        "data" : [ 
            {
                "id" : "11",
                "saleValue": 1000
            }, 
            {
                "id" : "112",
                "saleValue": 1400
            }, 
            {
                "id" : "22",

            }, 
            {
                "id" : "234",
                "saleValue": 111
            }
        ],

    },
    "createdTime" : ISODate("2018-03-18T10:18:48.000Z")
}

文档:2

 {
        "_id" : 444,
        "message_count" : 4,
        "messages" : {
            "data" : [ 
                {
                    "id" : "444",
                    "saleValue" : 2060
                }, 
                {
                    "id" : "444",
                }, 
                {
                    "id" : 234,
                    "saleValue" : 260
                }, 
                {
                    "id" : "34534",
                }
            ]
        },

        "createdTime" : ISODate("2018-03-18T03:11:50.000Z")
    }

所需的输出:

{
   total : 4831
}

我的查询:

db.getCollection('myCollection').aggregate([
    {
        "$group": {
            "_id": "$Id",

            "totalValue": {
                $sum: {
                    $sum: "$messages.data.saleValue"
                }
            }

        }
    }
])

因此，请尽可能帮助我解决此问题.预先感谢

So please if possible help me to solve this problem. Thanks in advance

推荐答案

由于汇总了集合中的所有文档，因此无法正常工作；您要对常量"_id": "tempId"进行分组，则只需通过添加$来引用正确的键即可:

It's not working correctly because it is aggregating all the documents in the collection; you are grouping on a constant "_id": "tempId", you just need to reference the correct key by adding the $ as:

db.getCollection('myCollection').aggregate([
    { "$group": {
        "_id": "$tempId",
        "totalValue": { 
            "$sum": { "$sum": "$messages.data.value" } 
        }
    } }
])

本质上是聚合操作的单阶段管道版本，带有一个额外的字段，该字段在组管道之前保存求和表达式，然后将该字段称为

which in essence is a single stage pipeline version of an aggregate operation with an extra field that holds the sum expression before the group pipeline then calling that field as the $sum operator in the group.

由于 $sum $group 阶段以及在 返回数字[120, 1200]的列表，然后将其用作

The above works since $sum from MongoDB 3.2+ is available in both the $project and $group stages and when used in the $project stage, $sum returns the sum of the list of expressions. The expression "$messages.data.value" returns a list of numbers [120, 1200] which are then used as the $sum expression:

db.getCollection('myCollection').aggregate([
    { "$project": {
        "values": { "$sum": "$messages.data.value" },
        "tempId": 1,
    } },
    { "$group": {
        "_id": "$tempId",
        "totalValue": { "$sum": "$values" }
    } }
])

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