正在从一个 table 中获取数据到 MongoDb 中的另一个

Question

我在 mongo 中有一个名为“sell”的数据库。现在这个 DB 包含两个 tables“Car”和“Order”。在“汽车”table 中，我有一个名为“价格”的属性。现在当我执行

db.Order.aggregate([ 
{
                    $lookup: {
                        from: "Car",
                        localField: "carId",
                        foreignField: "_id",
                        as: "PRICE",
                    },
                },
                { $unwind: "$PRICE" },]).pretty()

mongo shell 中的命令它给出包含“Order”table 属性的输出以及包含“Car”table 的所有属性的 PRICE 数组。现在，我想获取“Car”table 中的“price”属性。我当前的输出如下面的 link 所示，但我想从“价格”中获取“价格”。那么我的命令应该是什么？？？

我的“汽车”table 型号代码是

module.exports = {
    tableName: "Car",
    schema: true,
    attributes: {
        carmodel: {
            type: "String",
        },
        stock: {
            type: "Number",
        },
        color: {
            model: "Master",
        },
        code: {
            type: "STRING",
            unique: true,
        },
        brakes: {
            type: "String",
        },

        description: {
            type: "String",
        },
        wheels: {
            type: "String",
        },
        carwindow: {
            type: "String",
        },
        carseat: {
            model: "Master",
        },
        engine: {
            type: "String",
        },
        price: {
            type: "Number",
        },
        //self relation
        parentId: {
            model: "Car",
            columnName: "parentId",
        },
        //OTM
        Master: {
            collection: "Master",
            via: "car",
        },
        //OTO
        order: {
            collection: "order",
            via: "carId",
        },
        sellprice: {
            collection: "order",
            via: "price",
        },
    },
};

我的“订单”代码 table 是

const { date } = require("faker");
const Car = require("../models/Car");

module.exports = {
    tableName: "Order",
    schema: true,
    attributes: {
        address: { type: "String" },
        status: {
            model: "Master",
        },
        orderDate: { type: "string", columnType: "datetime" },
        //OTO
        carId: {
            model: "Car",
            unique: true,
        },
        price: {
            model: "Car",
            unique: true,
        },
        //OTM
        Master: {
            collection: "Master",
            via: "order",
        },
    },
};

我想要的输出是

{"PRICE" : 905000 }

PRICE 是订单中所有汽车价格的总和

https://i.stack.imgur.com/sJYDT.jpg

Answer 1

db.Order.aggregate([
    {
        $lookup: {
            from: "Car",
            let: { carId: "$carId" },
            pipeline: [
                { $match: { $expr: { $eq: ["$$carId", "$_id"] } } },
                { $project: { price: 1, _id: 0 } },
            ],
            as: "carInfo",
        },
    },
    { $unwind: "$carInfo" },
    { $replaceRoot: { newRoot: "$carInfo" } },
]);

正在从一个 table 中获取数据到 MongoDb 中的另一个

Fetching data from one table to another in MongoDb

javascript

database

mongodb

node.js

sails.js