MONGODB， NODEJS聚合简单例子

Mongodb 聚合

所需mongodb 本地 安装
node js 本地安装

程序分析

其实也没什么分析。代码说明了一切

var mongoose = require('mongoose'); //mongoo中间件
var Schema = mongoose.Schema; //数据模型

//Database connection 数据库连接
var uristring = 'mongodb://localhost/test'; 
var mongoOptions = {};

mongoose.connect(uristring, mongoOptions, function (err, res) {
  if (err) {
    console.log('Error when connecting to: ' + uristring + '. ' + err);
  }
  else {
    console.log('Successfully connected to: ' + uristring);
  }
});

//建立两个模型。Record, Account
//First let's create the Schemas:
// Record Schema
var Record = new Schema({
  amount: { type: Number, required: true },
  date: { type: Date, required: true },
  description: { type: String }
})

// Account Schema
var Account = new Schema({
  name: { type: String, required: true },
  currency: { type: String, required: true },
  created: { type: Date, default: Date.now },
  records: [Record]//嵌套Record模型
});

//Define Models
var AccountModel = mongoose.model('Account', Account);
var RecordModel = mongoose.model('Record', Record);
var ObjectId = require('mongoose').Types.ObjectId;

// Utility functions to insert data: 插入测试数据.
//一条数据叫：DOCUMENT
var insertAccount = function (account, callback) {
  var Account = new AccountModel();
  Account.name = account.name;
  Account.currency = account.currency;
  Account.records = []; 
  Account.save(function (err) {
    if (err) {
      console.log(err);
      return null;
    }
    return callback(Account._id);//完成插入之后的回调
  });
}

//根据所给accountId, 插入多个Record
//一个Account模型可以插入多个Record
var insertRecords = function (accountId, record, numberOfRecords, callback) {
  AccountModel.findOne({ _id: accountId }, function (err, account) {
    if (err) {
      console.log(err);
      return;
    }
    for (var i = 0; i < numberOfRecords; i++) {
      var Record = new RecordModel();
      Record.amount = record.amount;
      Record.date = new Date();
      Record.is_expense = record.is_expense;
      account.records.push(Record);
    }
    account.save(function (err2) {
      if (err2) {
        console.log(err2);
      }
      return callback();
    });
  });
}

//查询数据库的整个COLLECTION。未用到
var listAccounts = function () {
  var query = AccountModel.find();
  query.exec(function (err, accounts) {
    if (err) {
      console.log(err);
    }
    console.log(accounts);
  });
}

//查询单个DOCUMENT
var listAccount = function (id) {
  if (id == null) {
    return;
  }
  var query = AccountModel.find({ _id: id });
  query.field('_id name currency date');
  query.exec(function (err, accounts) {
    if (err) {
      console.log(err);
    }
    console.log(accounts);
  });
}

//移除单个document。未用到
var removeAccount = function (accountId) {
  var query = AccountModel.findOne({ _id: accountId });
  query.exec(function (err, account) {
    if (err) {
      console.log(err);
      return;
    }
    account.remove();
  });
}

//Aggregation function 聚合查询balance
var getBalance = function (accountId) {
  AccountModel.aggregate([
    {//先是匹配，匹配字段为accountId
      $match: {
        _id: accountId
      }
    },//多个动作
    { $unwind: "$records" },//查询完成之后回绕
    {
      $group: {//聚合数据
        _id: "$_id",按条件聚合。字段依然为_id。整个collection了
        //计算SUM。计算字段为account.records.amount
        balance: { $sum: "$records.amount" }
      }
    }
  ], function (err, result) {//回调包括出错和结果
    if (err) {
      console.log(err);
      return;
    }
    console.log(result);
  });
}

//Let's add some data and call the getBalance fucntion
//插入一条account数据
insertAccount({ name: "First Account", currency: "Dollar" }, function (accountId) {
  if (accountId == null) {
    console.log("accountId is null");
    return;
  }

//以上插入完成之后得到accountId。
//根据该accountId，插入1000条Record数据
  insertRecords(accountId, { amount: 123.5 }, 1000, function () {
   //插入完成之后，查询并控制台打印balance
    getBalance(accountId);
  });
});
//疑问：干嘛要两次插入？ 完全可以一次插入完整数据

最后

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