子查询替换包裹在列表中collaction一种在集合体B MongoDB的关键

Question

我有MongoDB的查询问题值

有2个集合在我的数据库，名称status和menu

在status主键_id对于买表的值menu收集

外键对于status集合：

{ 
    "_id": "green", "description": "running" 
} 
{ 
    "_id": "yellow", "description": "prepareing" 
} 
{ 
    "_id": "black", "description": "closing" 
} 
{ 
    "_id": "red", "description": "repairing" 
} 

对于menu集合：

{ 
    "name": "tony", 
    "bought": [ 
     { 
      "notebook": "green" 
     }, 
     { 
      "cellphone": "red" 
     } 
    ] 
} 
{ 
    "name": "andy", 
    "bought": [ 
     { 
      "fan": "black" 
     } 
    ] 
} 

我怎样才能查询得到以下答案吗？

（只需更换description为_id）

{ 
    "name": "tony", 
    "bought": [ 
     { 
      "notebook": "running" 
     }, 
     { 
      "cellphone": "repairing" 
     } 
    ] 
} 

是它的NoSQL子查询问题？我如何使用关键词来谷歌？

Answer 1

下面是使用聚合版本：

我们先从$unwind阶段提取一个单独的行

然后，$objectToArray各买正常化买场。

然后我们可以执行$lookup加入状态。

然后我们使用$group按名称

而且$arrayToObject重新集结到复位买了非规范化的风格

> db.menu.find() 
{ "_id" : ObjectId("5a102b0b49b317e3f8d6268b"), "name" : "tony", "bought" : [ { "notebook" : "green" }, { "cellphone" : "red" } ] } 
{ "_id" : ObjectId("5a102b0b49b317e3f8d6268c"), "name" : "andy", "bought" : [ { "fan" : "black" } ] } 
> db.status.find() 
{ "_id" : "green", "description" : "running" } 
{ "_id" : "yellow", "description" : "prepareing" } 
{ "_id" : "black", "description" : "closing" } 
{ "_id" : "red", "description" : "repairing" } 
> db.menu.aggregate([ 
{$unwind: '$bought'}, 
{$project: {name: 1, bought: {$objectToArray: '$bought'}}}, {$unwind: '$bought'}, 
{$lookup: {from: 'status', localField: 'bought.v', foreignField: '_id', as: "status"}}, 
{$project: {name: 1, bought: ["$bought.k", { $arrayElemAt: ["$status.description", 0]}]}}, 
{$addFields: {b: {v: {$arrayElemAt: ['$bought', 1]}, k: { $arrayElemAt: ['$bought', 0]}}}}, 
{$group: {_id: { name: '$name', _id: "$_id"}, b: {$push: "$b"}}},  
{$project: {_id: "$_id._id", name: "$_id.name", bought: {$arrayToObject: "$b"}}} 
]) 
{ "_id" : ObjectId("5a102b0b49b317e3f8d6268c"), "name" : "andy", "bought" : { "fan" : "closing" } } 
{ "_id" : ObjectId("5a102b0b49b317e3f8d6268b"), "name" : "tony", "bought" : { "notebook" : "running", "cellphone" : "repairing" } } 

我认为它可以在simplier的方式进行，但我不知道如何（我很高兴知道）。