MongoDB Introduction Practice Questions with Solutions

By /

Introduction

MongoDB is a popular NoSQL database used to store data in flexible, document-based structures. Instead of storing information in traditional rows and columns, MongoDB stores data as documents similar to JSON. In this chapter, you will practice basic MongoDB concepts such as databases, collections, documents, BSON, and simple commands. These examples are designed for beginners who are starting MongoDB from zero. MongoDB Introduction Practice Questions with Solutions to help you understand the concepts.

1. Check Whether MongoDB Is Available

Problem Statement

You have installed MongoDB and want to check whether the MongoDB Shell (mongosh) is available on your computer.

MongoDB Command / Query

mongosh --version

Expected Output

2.x.x

The exact version number may be different on your computer.

Explanation

The mongosh --version command displays the installed MongoDB Shell version.

If a version number appears, mongosh is available.

2. Connect to MongoDB

Problem Statement

Connect to a MongoDB server running on your local computer.

MongoDB Command / Query

mongosh

Expected Output

Connecting to: mongodb://127.0.0.1:27017/
...
test>

Explanation

Running mongosh starts the MongoDB Shell and connects to the MongoDB server running locally.

The prompt:

test>

means you are currently working with the test database.

3. Display the Current Database

Problem Statement

After opening MongoDB Shell, find out which database you are currently using.

MongoDB Command / Query

db

Expected Output

test

Explanation

The db command displays the name of the current database.

MongoDB commonly starts you in the test database when you open the shell without selecting another database.

4. Create or Switch to a Database

Problem Statement

Create or switch to a database named school.

MongoDB Command / Query

use school

Expected Output

switched to db school

Explanation

The use command selects a database.

use school

If school already exists, MongoDB switches to it.

If it does not exist, MongoDB selects it, but the database is generally created only when you store data in it.

You can check the current database with:

db

Output:

school

5. Show Available Databases

Problem Statement

You want to see the databases currently available in your MongoDB server.

MongoDB Command / Query

show dbs

Expected Output

admin    40.00 KiB
config   72.00 KiB
local    72.00 KiB
school   40.00 KiB

The exact sizes and database names can differ.

Explanation

The show dbs command displays databases that currently contain stored data and that the connected user can access.

MongoDB also has built-in databases such as admin, config, and local.

6. Create a Collection

Problem Statement

Create a collection named students inside the current school database.

MongoDB Command / Query

db.createCollection("students")

Expected Output

{ ok: 1 }

Explanation

A MongoDB collection is similar to a table in a relational database.

The command:

db.createCollection("students")

creates a collection called students.

The collection belongs to the currently selected database.

You can check the collections with:

show collections

Expected output:

students

7. Insert Your First MongoDB Document

Problem Statement

Insert one student into the students collection with the name Rahul, age 14, and course Python.

MongoDB Command / Query

db.students.insertOne({
    name: "Rahul",
    age: 14,
    course: "Python"
})

Expected Output

{
  acknowledged: true,
  insertedId: ObjectId('...')
}

Explanation

insertOne() is used to insert a single document into a collection.

The document contains three fields:

{
    name: "Rahul",
    age: 14,
    course: "Python"
}

MongoDB automatically generates a unique _id value if you do not provide one.

The _id helps MongoDB uniquely identify the document.

8. Display Documents from a Collection

Problem Statement

Display all students stored inside the students collection.

MongoDB Command / Query

db.students.find()

Expected Output

[
  {
    _id: ObjectId('...'),
    name: 'Rahul',
    age: 14,
    course: 'Python'
  }
]

Explanation

The find() method retrieves documents from a collection.

Here:

db.students.find()

means:

  • db → current database
  • students → collection
  • find() → retrieve documents

MongoDB displays the automatically generated _id along with the fields you inserted.

9. Insert Multiple Documents

Problem Statement

Add three more students to the students collection.

MongoDB Command / Query

db.students.insertMany([
    {
        name: "Priya",
        age: 15,
        course: "Java"
    },
    {
        name: "Aman",
        age: 16,
        course: "JavaScript"
    },
    {
        name: "Neha",
        age: 14,
        course: "MongoDB"
    }
])

Expected Output

{
  acknowledged: true,
  insertedIds: {
    '0': ObjectId('...'),
    '1': ObjectId('...'),
    '2': ObjectId('...')
  }
}

Explanation

insertMany() allows you to insert multiple documents at the same time.

Here, three student documents are inserted into the students collection.

You can now check the collection:

db.students.find()

You should see four students in total if you also completed Question 7.

10. Find a Specific Student

Problem Statement

Find the student whose name is Neha.

MongoDB Command / Query

db.students.findOne({
    name: "Neha"
})

Expected Output

{
  _id: ObjectId('...'),
  name: 'Neha',
  age: 14,
  course: 'MongoDB'
}

Explanation

findOne() searches for a single document that matches the specified condition.

Here:

{
    name: "Neha"
}

is the search condition.

MongoDB looks inside the students collection and returns the first matching document.

The important difference is:

find()

is commonly used to retrieve matching documents, while:

findOne()

returns a single matching document.

Key Takeaways

  • MongoDB is a NoSQL, document-oriented database.
  • MongoDB stores data in documents.
  • Documents are grouped inside collections.
  • Collections are stored inside databases.
  • mongosh is the MongoDB Shell.
  • db shows the current database.
  • use databaseName switches to a database.
  • show dbs displays available databases.
  • show collections displays collections in the current database.
  • insertOne() inserts one document.
  • insertMany() inserts multiple documents.
  • find() retrieves documents.
  • findOne() retrieves one matching document.
  • MongoDB automatically creates an _id for a document when one is not provided.

FAQs

1. What is MongoDB?

MongoDB is a NoSQL database that stores data as flexible documents instead of traditional rows and columns.

2. Is MongoDB a programming language?

No. MongoDB is a database system, not a programming language. You can use programming languages such as JavaScript, Python, Java, C#, and others to work with MongoDB.

3. What is a document in MongoDB?

A document is an individual record stored in MongoDB. It contains fields and values and is similar in structure to a JSON object.

4. What is a collection in MongoDB?

A collection is a group of MongoDB documents. It is broadly similar to a table in a relational database.

5. What is BSON in MongoDB?

BSON stands for Binary JSON. MongoDB uses BSON to store documents internally. BSON supports additional data types that are not available in standard JSON, such as ObjectId and date types.

6. What is the difference between find() and findOne() in MongoDB?

find() is used to retrieve matching documents, while findOne() returns a single matching document.

7. Can MongoDB create a database automatically?

Yes. MongoDB can create a database when you select a new database and then store data in it. Simply running use databaseName does not necessarily create a visible database until data is stored.

Written by Shubhranshu Shekhar, who has trained 20000+ students in coding.

Related Posts

Scroll to Top