MongoDB聚合$divide

Question

我是javascript的新手。我想计算平均销售额(averageSales = totalSales/ numOrders)。然而，我遇到了一些困难。如果有任何帮助或指导，我将非常感激。

const averageSale = await Order.aggregate([
        {
          $group: {
            _id: null,
            totalSales: { $sum: '$totalPrice' },
            numOrders: { $sum: 1 },
          },
        },
        {$project:{totalSales:1, numOrders:1, averagesale: { $divide: ['$totalSales', '$numOrders']}}},
      ]);

以下是我的一些文档

import express from 'express';
import expressAsyncHandler from 'express-async-handler';
import Order from '../models/orderModel.js';
import User from '../models/userModel.js';
import Product from '../models/productModel.js';
import { isAdmin, isAuth } from '../utils.js';



const orderRouter = express.Router();
orderRouter.get(
    '/',
    isAuth,
    isAdmin,
    expressAsyncHandler(async (req, res) => {
      const orders = await Order.find({}).populate('user', 'name');
      res.send(orders);
    })
  );
orderRouter.get(
    '/mine',
    isAuth,
    expressAsyncHandler(async (req, res) => {
      const orders = await Order.find({ user: req.user._id });
      res.send(orders);
    })
  );
  
  orderRouter.get(
    '/summary',
    isAuth,
    isAdmin,
    expressAsyncHandler(async (req, res) => {
      const orders = await Order.aggregate([
        {
          $group: {
            _id: null,
            numOrders: { $sum: 1 },
            totalSales: { $sum: '$totalPrice' },
          
          },
        },
      ]);
      const users = await User.aggregate([
        {
          $group: {
            _id: null,
            numUsers: { $sum: 1 },
          },
        },
      ]);
      const dailyOrders = await Order.aggregate([
        {
          $group: {
            _id: { $dateToString: { format: '%Y-%m-%d', date: '$createdAt' } },
            orders: { $sum: 1 },
            sales: { $sum: '$totalPrice' },
          },
        },
        { $sort: { _id: 1 } },
      ]);
      const productCategories = await Product.aggregate([
        {
          $group: {
            _id: '$category',
            count: { $sum: 1 },
          },
        },
      ]);

      const productName = await Product.aggregate([
        {
          $group: {
            _id: '$name',
            count: { $sum: 1 },
          },
        },
      ]);

      const productBy = await Product.aggregate([
        {
          $group: {
            _id: '$qty',
            count: { $sum: 1 },
            name: { $sum: '$name' },
          },
        },
      ]);

      const averageSale = await Product.aggregate([
        {
          $group: {
            _id: null,
            totalSales: { $sum: '$totalPrice' },
            numOrders: { $sum: 1 },
          },
        },
        {$project:{totalSales:1, orders:1, averagesale: { $divide: ['$totalSales', '$numOrders']}}},
      ]);
      
      res.send({ users, orders, dailyOrders, productCategories, productName, productBy, averageSale });
    })
  );

import mongoose from 'mongoose';

const orderSchema = new mongoose.Schema(
  {
    orderItems: [
      {
        name: { type: String, required: true },
        qty: { type: Number, required: true },
        image: { type: String, required: true },
        price: { type: Number, required: true },
        product: {
          type: mongoose.Schema.Types.ObjectId,
          ref: 'Product',
          required: true,
        },
      },
    ],
    shippingAddress: {
      fullName: { type: String, required: true },
      address: { type: String, required: true },
      city: { type: String, required: true },
      postalCode: { type: String, required: true },
      country: { type: String, required: true },
    },
    paymentMethod: { type: String, required: true },
    paymentResult: {
        id: String,
        status: String,
        update_time: String,
        email_address: String,
      },
    itemsPrice: { type: Number, required: true },
    shippingPrice: { type: Number, required: true },
    taxPrice: { type: Number, required: true },
    totalPrice: { type: Number, required: true },
    user: { type: mongoose.Schema.Types.ObjectId, ref: 'User', required: true },
    isPaid: { type: Boolean, default: false },
    paidAt: { type: Date },
    isDelivered: { type: Boolean, default: false },
    deliveredAt: { type: Date },
  },
  {
    timestamps: true,
  }
);
const Order = mongoose.model('Order', orderSchema);
export default Order;

Answer 1

我假设你正在尝试找到平均销售价格，没有必要使用$divide，因为$avg可以完成这项工作。

如果这不是你要找的，我可以知道你说的calculate the average number of sales (averageSales = totalSales/ numOrders)是什么意思吗？

db.collection.aggregate({
  "$group": {
    "_id": null,
    "totalSales": {
      $sum: "$totalPrice"
    },
    "numOrders": {
      $sum: 1
    },
    "avgPrice": {
      "$avg": "$totalPrice"
    }
  }
})

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