Mongodb和Node Js

Question

How can i execute this mongodb query through node js (mongoose). i have two tables with the follwoing schemas, i want to fetch username and password from users table and fetch full name from the info table.

var infoSchema = mongoose.Schema({ khatam_id: String, user_id: String, fullname: String, });

var usersSchema = mongoose.Schema({ user_id: String, username: String, password: String, });

Answer 1

install mongoose in your machine

npm install mongoose

import mongoose lib

const mongoose = require('mongoose');
const Schema = mongoose.Schema, ObjectId = Schema.ObjectId;

connect to mongodb and create schema for your table

mongoose.connect('mongodb://localhost/myappdatabase');

const usersSchema = new Schema({
 _id: ObjectId,
 user_id: String,
 username: String,
 fullname: String
});

const Users = mongoose.model('Users', usersSchema );

Find user from "Users" table using mongo query

Users.find({<here you can write your mongo query>}, function (err, docs) {
  // docs.forEach
});

Answer 2

you have to use aggregate

db.users.aggregate([
{
   $lookup:
     {
       from: "info",
       localField: "user_id",
       foreignField: "_id",
       as: "userInfo"
     }
},
{ "$unwind": "$userInfo" },
])

Answer 3

i don't know if you're a hot shot but if you are you can use this.

userSchema.virtual('infos', 
 {
   ref: 'Info',
   localField: 'user_id',
   foreignField: 'user_id',
 })

Assuming u name you're infoSchema as Info model ,mongodb converts it to infos in case you didn't know thats why the virtual field will be called as infos ref obviously a reference to Info model localField is the field referring the userSchema unique id and foreignField is the field u are referring in the infoSchema which matches the unique value that localfield u mentioned . Finally, along with all the fields in your userSchema add this

{
toJSON: { virtuals: true },
toObject: { virtuals: true },
}

so when u query for user Give it a shot it really comes in handy. Note: it doesn't actually create a field in the database (virtual duh.) it just populates your response object for front end rendering which is actually better.

Answer 4

Connect to MongoDB: Make sure MongoDB service is running before the program execution.

 var mongoose = require("mongoose");
    mongoose.connect("mongodb://localhost:27017/your-database");
    mongoose.Promise = global.Promise;
    var connection = mongoose.connection;
    connection.once('open', function() {
       console.log('connected to database);

    });

    connection.on('error', function() {
      console.error('Mongoose connection error");

     });
    process.on('SIGINT', function() {
       mongoose.connection.close(function() {
       console.log('Mongoose connection disconnected due to app SIGINT.');
     });

   });

create user schema :

const Schema = mongoose.Schema;
    const usersSchema = new Schema({
     user_id: String,
     username: String,
     fullname: String
    });

  const Users = mongoose.model('Users', usersSchema );

Run Query like this:

 Users.findOne({query})
    .then(function(user){
      // do something
     })
    .catch(function(err){
      // handle error
     }) 

Answer 5

You can use this query to get those types of records what you want:

db.users.aggregate([
{  $lookup: {
       from: "info",
       localField: "user_id",
       foreignField: "user_id",
       as: "userInfo"}},
{ "$unwind": "$userInfo" }])

Answer 6

Assuming you know how to set setup mongoose and connect your database and only need the correct query let me share something i noticed with the models you provided. I don't think there is a need for 2 collections as you can store the same thing under one collection because it saves the time for lookup for the user data from info schema. So user schema can be

var usersSchema = mongoose.Schema({ 
  user_id: String, 
  username: String, 
  password: String,
  khatam_id: String,
  fullname: String
});

And using the following query you can get the user details

Users.findOne({})
.then(function(user){
  // do something
 })
.catch(function(err){
  // handle error
 }) 

This is much more efficient and faster compared to using aggregate queries or mongoose populate functions.

If the above method is not suitable for you you can try the mongoose populate function.

UserSchema = new mongoose.Schema({
    user_id: String,
    password: String,
},
// schema options: Don't forget this option
// if you declare foreign keys for this schema afterwards.
{
    toObject: {virtuals:true},
    // use if your results might be retrieved as JSON
    // see http://stackoverflow.com/q/13133911/488666
    //toJSON: {virtuals:true} 
});

UserInfoSchema = new mongoose.Schema({
  user_id: String,
  khatam_id: String,
  username: String,
  fullname: String,
});


// Foreign keys definitions

UserSchema.virtual('userDetails', {
  ref: 'UserInfoSchema',
  localField: 'user_id',
  foreignField: 'user_id',
  justOne: true // for many-to-1 relationships
});


// Models creation

var UserSchema = mongoose.model('UserSchema', UserSchema);
var UserInfoSchema = mongoose.model('UserInfoSchema', UserInfoSchema);


// Querying

UserSchema.find({...})
    // if you use select() be sure to include the foreign key field !
   .select({.... user_id ....}) 
   // use the 'virtual population' name
   .populate('userDetails')
   .exec(function(err, books) {...})