从MongoDB中的嵌套文档中提取唯一值

Question

数据库如下所示：

"INC" : {
                "SIIB" : {
                    "Description" : "Interest Income, Bank",
                    "Value" : 66.06941
                },
                "STIE" : {
                    "Description" : "Total Interest Expense",
                    "Value" : 6.90925
                },
                "ENII" : {
                    "Description" : "Net Interest Income",
                    "Value" : 59.16016

如何获得所有不同的描述？

Answer 1

您可能正在寻找这样的东西：

db.getCollection('pets').aggregate({
    $unwind: "$Annual" // flatten the "Annual" array into separate documents
}, {
    $project: { // transform "INC" subdocuments into key-value pair
        "inc": {
            $objectToArray: "$Annual.INC"
        }
    }
}, {
    $group: {  // get all distinct values across all documents
        "_id": null,
        "distinctValues": { $addToSet: "$inc.v.Description" }
    }
})

Answer 2

您可以尝试仅获取数组中的distinct / Unique描述。

db.getCollection('Authors').distinct("Annual.INC.SIIB.Description")

  

在Mongo GUI中测试。

样本文档：

{
    "_id" : ObjectId("5b6a9bf571ace9eea8e64a04"),
    "name" : "userName",
    "avatar" : "avtarDetail",
    "Annual" : [ 
        {
            "INC" : {
                "SIIB" : {
                    "Description" : "Interest Income, Bank",
                    "Value" : 66.06941
                },
                "STIE" : {
                    "Description" : "Total Interest Expense",
                    "Value" : 6.90925
                },
                "STIEE" : {
                    "Description" : "Total Interest Expense",
                    "Value" : 6.90925
                }
            }
        }
    ]
}

输出：

[
    "Interest Income, Bank"
]