MongoDB - 如何查询集合中的嵌套项? [英] MongoDB - how to query for a nested item inside a collection?

问题描述

我有一些看起来像这样的数据:

<预><代码>[{"_id" : ObjectId("4e2f2af16f1e7e4c2000000a"),广告商":[{"created_at" : ISODate("2011-07-26T21:02:19Z"),类别":Infinity Pro Spin Air Brush"，"updated_at" : ISODate("2011-07-26T21:02:19Z"),"lowered_name" : "conair","twitter_name": "","facebook_page_url": "",网址" : ""，"user_ids" : [ ],"blog_url": "",},

而且我认为这样的查询会给出广告商的 ID:

var start = new Date(2011, 1, 1);>var end = new Date(2011, 12, 12);>db.agencies.find( { "created_at" : {$gte : start , $lt : end} } , { _id : 1 , program_ids : 1 , 广告商 { name : 1 } } ).limit(1).toArray();

但我的查询无效.知道如何将嵌套元素内的字段添加到我想要获取的字段列表中吗?

谢谢！

解决方案

使用点表示法(例如 advertisers.name)从嵌套对象中查询和检索字段:

db.agencies.find({advertisers.created_at":{$gte:开始，$lt: 结束}},{_id: 1,program_ids: 1,advertisers.name":1}}).limit(1).toArray();

参考:检索字段子集和 点符号

I have some data that looks like this:

[
    {
        "_id" : ObjectId("4e2f2af16f1e7e4c2000000a"),
        "advertisers" : [
            {
                "created_at" : ISODate("2011-07-26T21:02:19Z"),
                "category" : "Infinity Pro Spin Air Brush",
                "updated_at" : ISODate("2011-07-26T21:02:19Z"),
                "lowered_name" : "conair",
                "twitter_name" : "",
                "facebook_page_url" : "",
                "website_url" : "",
                "user_ids" : [ ],
                "blog_url" : "",
            },

and I was thinking that a query like this would give the id of the advertiser:

var start  = new Date(2011, 1, 1);
> var end  = new Date(2011, 12, 12);
> db.agencies.find( { "created_at" : {$gte : start , $lt : end} } , { _id : 1 , program_ids : 1 , advertisers { name : 1 }  } ).limit(1).toArray();

But my query didn't work. Any idea how I can add the fields inside the nested elements to my list of fields I want to get?

Thanks!

解决方案

Use dot notation (e.g. advertisers.name) to query and retrieve fields from nested objects:

db.agencies.find({
 "advertisers.created_at": {
   $gte: start,
   $lt: end
  }
 },
{
 _id: 1,
  program_ids: 1,
  "advertisers.name": 1
 }
}).limit(1).toArray();

Reference: Retrieving a Subset of Fields and Dot Notation

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