如何从mongodb中的同一集合查询大于不同文档中的值？

问题描述

我有一个如下的销售货款。我想使用mongo shell进行查询以查找价格超过20的产品详细信息。

[{
  "Customer_Info":{
        "Customer_Id": 1,"First_Name": "John","Last_Name": "Smith","Address": "Sydney","State": "Sydney","Postcode": "0920","Phone": "0143464663"
  },"Order_Info": [
    {
      "Order_Id": 1,"Order_Date": "01-01-2020","Delivery_Date": "01-01-2020","Line_Info": [
        {
          "Line_Id": 1,"Line_Price": 100,"Line_Units_Added": 2,"Product_Info": {
            "Product_Id": 300,"Product_Name": "Orange","Product_Description": "Fruit","Number_in_Stock": 50,"Product_Weight": 1,"Product_Cost": 300,"Product_in_Date": "01-01-2020","Product_Type": "Fruits","Farmer_Info": {
              "Farmer_Id": 123,"Farmer_First_Name": "Drake","Farmer_Last_Name": "Levine","Farmer_Address": "Sydney","Farmer_State": "Sydney","Farmer_Post_Code": "1200"
            }
          }
        },{
          "Line_Id": 5,"Line_Price": 25,"Line_Units_Added": "1","Product_Info": {
            "Product_Id": 305,"Product_Name": "Banana","Number_in_Stock": 100,"Product_Cost": 100,{
          "Line_Id": 6,"Product_Name": "Jackfruit","Number_in_Stock": 20,"Product_Cost": 50,{
          "Line_Id": 7,"Line_Price": 200,"Line_Units_Added": 1,"Product_Info": {
            "Product_Id": 310,"Product_Name": "Dragon Fruit","Number_in_Stock": 10,"Product_Cost": 2,"Farmer_Post_Code": "1200"
            }
          }
        }
      ]
    },{
      "Order_Id": 2,"Line_Info": [
        {
          "Line_Id": 2,"Product_Info": {
            "Product_Id": 301,"Product_Name": "Mango","Product_Cost": 500,"Farmer_Post_Code": "1200"
            }
          }
        }
      ]
    }
  ]
},{
  "Customer_Info":{
  "Customer_Id": 2,"First_Name": "Popeye","Last_Name": "Sailorman","Phone": "123456"},"Order_Info": [
    {
      "Order_Id": 3,"Line_Info": [
        {
          "Line_Id": 3,"Line_Price": 50,"Line_Units_Added": 5,"Product_Info": {
            "Product_Id": 500,"Product_Name": "Spinach","Product_Description": "vegetables","Number_in_Stock": 30,"Product_Weight": 1.5,"Product_Cost": 30,"Product_Type": "Veg","Farmer_Info": {
              "Farmer_Id": "420","Farmer_First_Name": "Olive","Farmer_Last_Name": "Lewine","Farmer_Post_Code": "1200"
            }
          }
        }
      ]
    }
  ]
}]

要使用mongo shell查找大于20的产品名称和产品成本。我已经完成了以下操作：

db.sales.find( { "Order_Info.Line_Info.Product_Info.Product_Cost": { $gt: 20} },{"_id": 0,"Order_Info.Line_Info.Product_Info.Product_Name": 1,"Order_Info.Line_Info.Product_Info.Product_Cost": 1} ).pretty();

但是不幸的是，它仅返回第一个文档值。如何实现？

解决方法

您可以通过聚合来实现

1. $map帮助处理数组中的每个元素
2. $filter帮助使用条件和过滤器

Mongo脚本

[
  {
    $project: {
      Order_Info: {
        $map: {
          input: "$Order_Info",in: {
            $filter: {
              input: "$$this.Line_Info",cond: {
                $gt: [
                  "$$this.Product_Info.Product_Cost",30
                ]
              }
            }
          }
        }
      }
    }
  }
]

工作Mongo playground