Question

我是MongoDB的新手。我在MongoDB中有以下集合。我的问题是我无法根据提供的ID或名称创建一个提供所需设施的查找命令。

查找我尝试过但不工作的命令： -

db.mgh_facilities.find({facilities: {$elemMatch: {name: "Foreign exchange assistance"}}}).

对我而言，它返回所有记录。不应该只是返回{“id”：“11”，“name”：“外汇援助”}

我的收藏： -

{
    "_id" : ObjectId("548acc28ae6ff1c0fd1d7470"),
    "responseCode" : "true",
    "facilities" : [ 
        {
            "id" : "11",
            "name" : "Foreign exchange assistance"
        }, 
        {
            "id" : "12",
            "name" : "Assistance with luggage on request"
        }, 
        {
            "id" : "13",
            "name" : "24 hours power back-up"
        }, 
        {
            "id" : "14",
            "name" : "A/C Power Backup Available"
        }, 
        {
            "id" : "15",
            "name" : "swimming pool"
        }, 
        {
            "id" : "35",
            "name" : "shoe cleaning service"
        }, 
        {
            "id" : "36",
            "name" : "Smoke detectors"
        }, 
        {
            "id" : "37",
            "name" : "Fire Extinguishers in each room"
        }, 
        {
            "id" : "38",
            "name" : "Pest Control"
        }, 
        {
            "id" : "39",
            "name" : "Conference / Banquet Hall"
        }, 
        {
            "id" : "45",
            "name" : "Restaurant"
        }, 
        {
            "id" : "53",
            "name" : "Anti-slip ramps"
        }, 
        {
            "id" : "56",
            "name" : "Tea/ Coffee Maker in the Rooms"
        }, 
        {
            "id" : "59",
            "name" : "Wi Fi Internet"
        }
   ]
}

Answer 1

find命令找到了包含设施对象的文档，其名称与您的搜索匹配。它不知道您只想查看负责该文档的单个子文档与您的搜索条件匹配。

您可以告诉mongo您希望使用位置$运算符来查看该元素。

db.mgh_facilities.find({"facilities.name": "Foreign exchange assistance"}, {"facilities.$": true})

Answer 2

你可以试试这个

db.mgh_facilities.aggregate([
{
    $unwind:"$facilities"    
},
{
    $match:{"facilities.name": "Foreign exchange assistance"}
},{
    $project:{
        _id:0,
        facilities:1
    }
}

])

结果：

{
    "result" : [ 
        {
            "facilities" : {
                "id" : "11",
                "name" : "Foreign exchange assistance"
            }
        }
    ],
    "ok" : 1
}

MongoDB：无法找到所需的记录

2 个答案: