MongoDB:找不到所需的记录

Question

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

查找我已经尝试但不起作用的命令：-

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

对我来说，它返回了所有记录。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 命令已找到包含名称与您的搜索匹配的设施对象的文档。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。

你可以告诉 mongo 你想用位置 $ 运算符看到那个元素。

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
}