mongodb - 聚合中 mongodb 中字段的组连接

Question

我收藏的文档，

{
    "_id" : "abc1",
    "Data" : {
        "Campaign Name" : "Campaign 1",
        "Ad Set Name" : "Adset 1",
        "Ad Name" : "Ad 1",
        "URL Tags" : "url tag 1"
    }
},
{
    "_id" : "abc2",
    "Data" : {
        "Campaign Name" : "Campaign 2",
        "Ad Set Name" : "Adset 1",
        "Ad Name" : "Ad 1",
        "URL Tags" : "url tag 1"
    }
},
{
    "_id" : "abc3",
    "Data" : {
        "Campaign Name" : "Campaign 2",
        "Ad Set Name" : "Adset 2",
        "Ad Name" : "Ad 2",
        "URL Tags" : "url tag 2"
    }
},
{
    "_id" : "abc4",
    "Data" : {
        "Campaign Name" : "Campaign 3",
        "Ad Set Name" : "Adset 1",
        "Ad Name" : "Ad 1",
        "URL Tags" : "url tag 1"
    }
}

在输出中需要这样的东西，

{
    "_id" : "Campaign 3",
    "total" : 60.0,
    "myField" : [ "url tag 1-Ad 1" ]
},
{
    "_id" : "Campaign 2",
    "total" : 120.0,
    "myField" : [ "url tag 1-Ad 1", "url tag 2-Ad 2" ]
},
{
    "_id" : "Campaign 1",
    "total" : 96.0,
    "myField" : [ "url tag 1-Ad 1" ]
}

到目前为止我做了什么(不成功的)，

db.adsets.aggregate([
    {$group:{_id:"$Data.Campaign Name",total:{$sum:1}}},
    {$project:{_id:1,total:1,myField:{$concat:["$Data.URL Tags","-","$Data.Ad Name"]}}}
],{explain:false});

目前正在输出中，

{
    "_id" : "Campaign 3",
    "total" : 60.0,
    "myField" : null
},
{
    "_id" : "Campaign 2",
    "total" : 120.0,
    "myField" : null
},
{
    "_id" : "Campaign 1",
    "total" : 96.0,
    "myField" : null
}

我不知道我做错了什么，这就是为什么我在 myField 中得到的是空值而不是串联字符串。请帮忙!!提前致谢。

Answer 1

您可以连接所需的值并在分组期间推送到数组:

db.adsets.aggregate([
    {$group:{
        _id:"$Data.Campaign Name",
        total : {$sum:1},
        myfield: {$push: {$concat:["$Data.URL Tags", "-", "$Data.Ad Name"]}}
        }
    }]
)

这应该会像您提到的那样给出输出。
(正如您在问题评论中提到的， myfield 字段将是您需要的数组，而不是像初始问题那样的对象)

如果你不希望连接的值在相同时出现两次，你可以使用 $addToSet 而不是 push

db.adsets.aggregate([
    {$group:{
        _id:"$Data.Campaign Name",
        total : {$sum:1},
        myfield: {$addToSet: {$concat:["$Data.URL Tags", "-", "$Data.Ad Name"]}}
        }
    }]
)