嵌套的 Mongo DB 查询

如何解决嵌套的 Mongo DB 查询

我想计算利润，我需要获取项目 JsonArray，它是其他嵌套 JsonArray 订单的一部分

为了获取订单数组对象，我们可以使用这个查询

var mapProfit=function(){for(var i in this.order)emit(this.order[i],1)}
var redProfit=function(k,v){return Array.sum(v)}
db.OnlineGrocery.mapReduce(mapProfit,redProfit,{out:"Result"}).find()

如何使用此查询来获取项目

{ 
    "_id" : ObjectId("605ac4dcf77f914c2aab81b0"),"customer_id" : NumberInt(1),"customer_firstName" : "Lannie","customer_lastName" : "Chazerand","customer_email" : "lchazerand0@usnews.com","customer_phoneNumber" : "3862602788","address" : [
        {
            "street" : "00523 Helena Plaza","city" : "Cincinnati","province" : "Ohio"
        }
    ],"order" : [
        {
            "order_id" : "98-037-3943","order_date" : "6/22/2020","item" : [
                {
                    "item_id" : NumberInt(1),"item_name" : "Appetizer - Mango Chevre","item_desc" : "Nondisp fx of pisiform,unsp wrist,init for clos fx","item_qty" : NumberInt(5),"item_actual_price" : "$2.78","item_selling_price" : "$8.23"
                },{
                    "item_id" : NumberInt(2),"item_name" : "Pork - Bacon,back Peameal","item_desc" : "Other cervical disc disorders at C6-C7 level","item_qty" : NumberInt(2),"item_actual_price" : "$1.53","item_selling_price" : "$6.71"
                }
         ]
    }]
}

解决方法

您可以使用点或括号表示法访问 JSON 对象，但由于 order 属性包含一个对象数组，因此您必须先访问数组索引，然后才能访问数组内的对象属性。在这种情况下，它看起来像 order[index0].item[selectedItemIndex].item_qty/anyOtherItemProperty

希望这会有所帮助，否则请提供有关您的问题的更多详细信息。

MapReduce 可能不是您计算利润所需的工具。

为了获得整体利润，您可以简单地将订单和商品平仓，然后总结一下：

db.collection.aggregate([
  {$unwind: "$order"},{$unwind: "$order.item"},{$group: {
      _id: null,profit: {
        $sum: {
          $subtract: [
            {$toDecimal: {
                $trim: {
                  chars: {$literal: "$"},input: "$order.item.item_selling_price",}
            }},{$toDecimal: {
                $ltrim: {
                  input: "$order.item.item_actual_price",chars: {$literal: "$"}
                }
            }}
          ]
        }
      }
  }}
])

Playground

或者，如果您需要每件商品或每笔订单的利润，则需要几个小组阶段：

db.collection.aggregate([
  {$unwind: "$order"},{$addFields: {
      "order.item.profit": {
        $subtract: [
            {$toDecimal: {
              $trim: {
                chars: {$literal: "$"},{$toDecimal: {
              $ltrim: {
                input: "$order.item.item_actual_price",chars: {$literal: "$"}
              }
            }}
        ]
      }
  }},{$group: {
      _id: {
        _id: "$_id",order: "$order.order_id"
      },root: {$first: "$$ROOT"},items: {$push: "$order.item"},profit: {$sum: "$order.item.profit"}
  }},{$addFields: {
      "root.order.item": "$items","root.order.profit": "$profit"
  }},{$replaceRoot: {newRoot: "$root"}},{$group: {
      _id: "$_id",orders: {$push: "$order"}
   }},{$addFields: {"root.order": "$orders"}},{$replaceRoot: {newRoot: "$root"}}
])

Playground