node-mongoDB

连接数据库
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
  if (err) throw err;
  console.log("数据库已链接!");
  db.close();
});


创建集合
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017';
MongoClient.connect(url, { useNewUrlParser: true }, function (err, db) {
    if (err) throw err;
    console.log('数据库已连接');
    var dbase = db.db("runoob");
    dbase.createCollection('site', function (err, res) {
        if (err) throw err;
        console.log("创建集合!");
        db.close();
    });
});


数据插入（如果集合不存在，会自动创建集合）
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";

MongoClient.connect(url, { useNewUrlParser: true }, function (err, db) {
   if (err) throw err;
   console.log("数据库连接成功");
   var dbo = db.db("runoob");
   var myobj = { name: "baidu", url: "www.baidu.com" };
   dbo.collection("web").insertOne(myobj, function (err, res) {
      if (err) throw err;
      console.log("数据插入成功");
      db.close();
   });
});


数据插入（多条）
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";

MongoClient.connect(url, { useNewUrlParser: true }, function (err, db) {
   if (err) throw err;
   console.log("数据库连接成功");
   var dbo = db.db("runoob");
   var myobj = [
      { name: "baidu", url: "www.baidu.com" },
      { name: "google", url: "www.google.com" },
      { name: "bbb", url: "www.bilibili.com" }
];
   dbo.collection("web").insertMany(myobj, function (err, res) {
      if (err) throw err;
      console.log("数据插入成功"+res.insertedCount);
      db.close();
   });
});

查询
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
    if (err) throw err;
    var dbo = db.db("runoob");
     var whereStr = {"name":'baidu'};  // 查询条件
    dbo.collection("web").find(whereStr).toArray(function(err, result) {
        if (err) throw err;
        console.log(result);
        db.close();
    });
});


更新一条数据
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
    if (err) throw err;
    var dbo = db.db("runoob");
    var whereStr = {"name":'baidu'};  // 查询条件
    var updateStr = {$set: { "url" : "https://www.baiduxx.com" }};
    dbo.collection("web").updateOne(whereStr, updateStr, function(err, res) {
        if (err) throw err;
        console.log("数据更新成功");
        db.close();
    });
});


更新多条数据
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
    if (err) throw err;
    var dbo = db.db("runoob");
    var whereStr = {"url":'www.baidu.com'};  // 查询条件
    var updateStr = {$set: { "url" : "www.baidux2.com" }};
    dbo.collection("web").updateMany(whereStr, updateStr, function(err, res) {
        if (err) throw err;
         console.log(res.result.nModified + " 条数据被更新");
        db.close();
    });
});

输出一条数据
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
    if (err) throw err;
    var dbo = db.db("runoob");
    var whereStr = {"name":'bizhan'};  // 查询条件
    dbo.collection("web").deleteOne(whereStr, function(err, obj) {
        if (err) throw err;
        console.log("数据删除成功");
        db.close();
    });
});

删除多条数据
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
    if (err) throw err;
    var dbo = db.db("runoob");
    var whereStr = {"name":'baidu'};  // 查询条件
    dbo.collection("web").deleteMany(whereStr, function(err, obj) {
        if (err) throw err;
        console.log("数据删除成功");
        db.close();
    });
});


排序
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
    if (err) throw err;
    var dbo = db.db("runoob");
    var mysort = { url: 1 };
    dbo.collection("web").find().sort(mysort).toArray(function(err, result) {
        if (err) throw err;
        console.log(result);
        db.close();
    });
});


左联合

集合1：order

[
  { _id: 1, product_id: 154, status: 1 }
]
集合2：products

[
  { _id: 154, name: '笔记本电脑' },
  { _id: 155, name: '耳机' },
  { _id: 156, name: '台式电脑' }
]

代码
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://127.0.0.1:27017/";
 
MongoClient.connect(url, { useNewUrlParser: true }, function(err, db) {
  if (err) throw err;
  var dbo = db.db("runoob");
  dbo.collection('order').aggregate([
    { $lookup:
       {
         from: 'products',            // 右集合
         localField: 'product_id',    // 左集合 join 字段
         foreignField: '_id',         // 右集合 join 字段
         as: 'orderdetails'           // 新生成字段（类型array）
       }
     }
    ]).toArray(function(err, res) {
    if (err) throw err;
    console.log(JSON.stringify(res));
    db.close();
  });
});

执行结果
[{"_id":1,"product_id":154,"status":1,"orderdetails":[{"_id":154,"name":"手机"}]}]


其他很多（跟mongoDB的正常语法都是一样的）
mongoDB笔记： https://blog.csdn.net/u013761036/article/details/101054229

指定了返回的条数
dbo.collection("site").find().limit(2).toArray（
如果要指定跳过的条数
dbo.collection("site").find().skip(2).limit(2).toArray(
删除集合
dbo.collection("test").drop(