How to fetch data from multiple collections in MongoDB?

Question

How to fetch data from multiple collections in MongoDB by using a common field and sending data (in those fetched collections) using one response?

Employee Scheema:

   const mongoose = require("mongoose");

const employeeSchema = new mongoose.Schema(
  {
    profilePic: {
      type: String,
    },
    employeeID: {
      type: String,
      required: true,
    },
    employeeFirstName: {
      type: String,
      required: true,
    },
    employeeLastName: {
      type: String,
      required: true,
    },
    birthday: {
      type: String,
    },
    streetNo: {
      type: String,
    },
    city: {
      type: String,
    },
    phoneNumber: {
      type: String,
    },

    jobRole: {
      type: String,
      required: true,
    },
    NIC: {
      type: String,
      required: true,
      unique: true,
    },
    companyEmail: {
      type: String,
      required: true,
      unique: true,
    },
    status: {
      type: String,
      required: true,
    },

    resignDate: {
      type: String,
    },
    jobType: {
      type: String,
      required: true,
    },
    candidateID: {
      type: String,
      required: true,
    },
    teamID: {
      type: String,
    },
    lastSeen: {
      type: String,
    },
    token: {
      type: String,
    },
  },
  { timestamps: true }
);

module.exports = mongoose.model("employee", employeeSchema);

Acadamic Qualification Scheema:

const mongoose = require("mongoose");

const academicQualificaationSchema = new mongoose.Schema(
  {
    employeeID: {
      type: String,
      required: true,
    },

    ordinaryLevelResult: {
      type: Array,
      required: true,
    },
    advancedLevelResults: {
      type: Array,
      required: true,
    },

    achievements: {
      type: Array,
      required: true,
    },
  },
  { timestamps: true }
);

module.exports = mongoose.model(
  "academicQualification",
  academicQualificaationSchema
);

Professional Qualification Scheema:

const mongoose = require("mongoose");

const proffesionalQualificaationSchema = new mongoose.Schema(
  {
    employeeID: {
      type: String,
      required: true,
    },
    degree: {
      type: Array,
      required: true,
    },
    language: {
      type: Array,
      required: true,
    },
    course: {
      type: Array,
      required: true,
    },
  },
  { timestamps: true }
);

module.exports = mongoose.model(
  "proffesionalQualification",
  proffesionalQualificaationSchema
);

Controller:

exports.viewEmployees = async (req, res) => {
  try {
    let accQuali, profQuali;
    const employees = await employeeSchema.find();

    accQuali = await academicQualificaationSchema.find();

    profQuali = await ProffesionalQualificationSchema.find();

    if (employees || accQuali || profQuali) {
      return res.status(200).json({ data: { employees, profQuali, accQuali } });
    } else {
      return res.status(404).json({ message: message });
    }
  } catch (err) {
    return res.status(404).json({ err: err.message });
  }
};

This controller is working properly and sends all data in 3 collections with the use of one response. But, I am comfortable if I will be able to Fetch data separately for each employee.

please add the schemas, sample input and expected output. maybe $lookup is what you need — 1sina1
– 1sina1, Commented Apr 8, 2022 at 19:06
I edited the question including the schemas as per your request, thank you for responding. — Nimasha Madhushani
– Nimasha Madhushani, Commented Apr 8, 2022 at 19:23
Yes, solution was $lookup. Thank you for the support @1sina1 — Nimasha Madhushani
– Nimasha Madhushani, Commented Sep 21, 2022 at 15:02

nimrod serok · Accepted Answer · 2022-04-09 05:43:49Z

1

If you want to get the data from the three collections for specific employee or employees, you can use an aggregation pipeline with a $lookup stage, as suggested by @1sina1. For example:

db.employee.aggregate([
  {
    $match: {"employeeID": "IDA"}
  },
  {
    $lookup: {
      from: "academicQualification",
      localField: "employeeID",
      foreignField: "employeeID",
      as: "academicQualification"
    }
  },
  {
    $lookup: {
      from: "proffesionalQualification",
      localField: "employeeID",
      foreignField: "employeeID",
      as: "proffesionalQualification"
    }
  }
])

As you can see on the playground

answered Apr 9, 2022 at 5:43

nimrod serok

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2 Comments

nimrod serok Over a year ago

Is it working for you?

Nimasha Madhushani Over a year ago

Yes, It is working. Thank you for the support and sorry for the late reply..

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