20 MongoDB Quiz Questions and Answers

1. Question: What type of database is MongoDB?
Options:
A) Relational
B) Document-oriented
C) Key-value
D) Column-family
Answer: B
Explanation: MongoDB is a NoSQL database that uses a document-oriented model, storing data in flexible, JSON-like documents.

2. Question: Which command is used to insert a new document into a MongoDB collection?
Options:
A) db.collection.update()
B) db.collection.insertOne()
C) db.collection.delete()
D) db.collection.find()
Answer: B
Explanation: The db.collection.insertOne() method is specifically used to insert a single document into a collection in MongoDB.

3. Question: What is the purpose of the _id field in a MongoDB document?
Options:
A) To store the document’s size
B) To serve as a unique identifier
C) To indicate the document’s creation date
D) To link to another collection
Answer: B
Explanation: The _id field is a unique identifier for each document in a MongoDB collection, ensuring no duplicates.

4. Question: Which query operator is used to find documents where a field is greater than a specified value?
Options:
A) $eq
B) $lt
C) $gt
D) $ne
Answer: C
Explanation: The $gt operator in MongoDB queries is used to select documents where the value of a field is greater than the specified value.

5. Question: How does MongoDB handle schema?
Options:
A) Enforces a strict schema like relational databases
B) Uses a dynamic schema
C) Requires schema definition before insertion
D) Does not support schemas at all
Answer: B
Explanation: MongoDB uses a dynamic schema, allowing documents in the same collection to have different structures.

6. Question: What is sharding in MongoDB?
Options:
A) A method for data replication
B) A way to horizontally scale data across multiple servers
C) A backup strategy
D) A query optimization technique
Answer: B
Explanation: Sharding in MongoDB distributes data across multiple machines to support horizontal scaling and handle large datasets.

7. Question: Which method is used to update a single document in MongoDB?
Options:
A) db.collection.updateMany()
B) db.collection.updateOne()
C) db.collection.replaceOne()
D) db.collection.insertOne()
Answer: B
Explanation: The db.collection.updateOne() method updates a single document that matches the specified filter.

8. Question: What does the aggregation framework in MongoDB allow?
Options:
A) Only basic queries
B) Processing data records and returning computed results
C) Inserting multiple documents at once
D) Deleting collections
Answer: B
Explanation: The aggregation framework processes data from collections and performs operations like grouping, filtering, and computing aggregates.

9. Question: In MongoDB, what is an index?
Options:
A) A separate database
B) A structure that improves query performance
C) A type of document
D) A backup file
Answer: B
Explanation: Indexes in MongoDB are special data structures that speed up query operations by providing quick access to data.

10. Question: Which command creates a new database in MongoDB?
Options:
A) use databaseName
B) create database databaseName
C) db.createDatabase()
D) mongo create databaseName
Answer: A
Explanation: The use databaseName command switches to a specified database, creating it if it does not already exist.

11. Question: What is the default port for MongoDB server?
Options:
A) 8080
B) 27017
C) 3306
D) 5432
Answer: B
Explanation: MongoDB’s default listening port is 27017, which is used for client connections.

12. Question: How do you drop a collection in MongoDB?
Options:
A) db.collection.drop()
B) db.dropCollection(collectionName)
C) remove collectionName
D) delete collectionName
Answer: B
Explanation: The db.dropCollection(collectionName) method is used to remove a specified collection from the database.

13. Question: What is replication in MongoDB?
Options:
A) Copying data to another server for backup
B) Creating multiple copies of data across servers for high availability
C) Merging collections
D) Sharding data vertically
Answer: B
Explanation: Replication in MongoDB involves maintaining multiple copies of data on different servers to ensure availability and fault tolerance.

14. Question: Which operator is used for logical AND in MongoDB queries?
Options:
A) $or
B) $and
C) $nor
D) $not
Answer: B
Explanation: The $and operator combines multiple expressions, returning documents that match all conditions.

15. Question: What is MongoDB Compass?
Options:
A) A programming language
B) A graphical user interface for MongoDB
C) A query language
D) A data backup tool
Answer: B
Explanation: MongoDB Compass is a GUI tool that allows users to visualize and interact with MongoDB data without writing code.

16. Question: How can you sort query results in MongoDB?
Options:
A) Using the sort() method
B) Using the filter() method
C) Using the limit() method
D) Using the project() method
Answer: A
Explanation: The sort() method in MongoDB queries is used to sort the results of a cursor in ascending or descending order.

17. Question: What does the $in operator do in MongoDB?
Options:
A) Checks if a field is not equal to a value
B) Matches any value in an array
C) Selects documents where a field is in a specified array of values
D) Increments a field value
Answer: C
Explanation: The $in operator selects documents where the value of a field is equal to any value in the specified array.

18. Question: Which feature allows MongoDB to support multi-document transactions?
Options:
A) Sharding
B) Replication sets
C) ACID properties
D) Indexing
Answer: C
Explanation: MongoDB supports multi-document transactions with ACID properties, ensuring reliability in operations across multiple documents.

19. Question: What is the purpose of the mongod command?
Options:
A) To start the MongoDB server
B) To query data
C) To create indexes
D) To restore backups
Answer: A
Explanation: The mongod command is used to start the MongoDB daemon, which runs the database server.

20. Question: In MongoDB, how are embedded documents different from referenced documents?
Options:
A) Embedded documents are stored in a separate collection
B) Referenced documents are nested within the parent document
C) Embedded documents are stored within the parent document
D) They are the same thing
Answer: C
Explanation: Embedded documents are stored directly inside a parent document, while referenced documents link to another collection for normalization.