Join two collections using mongoose and get data from both

Question

I have two collections User and Taxdetails , I want the name and phone number from User and payment details from Taxdetails joingin on user_id in both collections.

I am doing this:

User
    .find()
    .exec(function(err, userDetails) {
        if (err) {
            console.log("error in user collection");
            res
                .status(400)
                .json({ 'message':'error','success':false });
        } else {
            var userid = userDetails.map(function(obj) { 
                return obj._id;
              });
              Taxdetail
                  .find()
                  .exec({ user_id : { $in : userid } },function(err, requests) {
                        if(err){
                            console.log("error in TaxDetails collection");
                            res
                                .status(400)
                                .json({ 'message':'error','success':false });
                        }else{
                            console.log("Success, got some data");
                            res
                                .status(200)
                                .json(requests);
                        }                     
                    });
        }
    });

Answer 1

You may want use referenced schema in your User schema and then populate it like this:

var taxDetailSchema = new Schema({
    title: String
});

var taxDetail = mongoose.model('taxDetail', taxDetailSchema);

var userSchema = new Schema({
  name:  String,
  taxDetails: [{ type: Schema.Types.ObjectId, ref: 'taxDetail' }]
});

Your query would look like this:

User
.find()
.populate('taxDetails')
.exec(function(err, users) {

});

The users should look like this:

[
    {
        name: 'Some Name',
        taxDetails: [
            { title: 'Some Title' },
            { title: 'Some other Title' }
        ]
    }
]

Mongoose documentation here

Hope it helps

Answer 2

Joining Two Collections In A Mongoose With Example

Simple and easy use populate

We will make Schema a user and another post as you see below

const { Schema, model} = require("mongoose");

const UserSchema = new Schema({
   name:{
      type: String,
      required: true
   },
   email:{
      type: String,
      required: true
   },
   posts:[{
      type: Schema.Types.ObjectId, ref: "Post"
   }]
});


const PostSchema = new Schema({
   title: String,
   desc: String,
   User: {type: Schema.Tpes.ObjectId, ref: "User"}
});

export const Post = model("Post", PostSchema);
export const User = model("User", UserSchema);

Then

try {
   const user = User.create({
      name:"Robert Look",
      email: "phpcodingstuff@gmail.com"
   })

   try {
      const post1 = Post.create({
         title: "This is a first post",
         desc: "this a a first description"
         user: User._id // assign the _id from the user
      });
   } catch (err) {
      console.log(err.message)
   }
} catch (err) {
   console.log(err.message)
}

Reading Models

User.findOne({
   name: "Robert Look"
}).populate('posts').exec((err, user) =>{
   if(err){
      console.log(err)
   }else{
      console.log(users.posts[0].desc)
   }
});

Conclusion

We saw above how to use populate We also saw how joining two documents in mongoose (MongoDB), if you write the query correctly then you will get a good result or your JSON.

More Information: Mongoose