1. Which type of database is MongoDB?
- a) Relational Database
- b) Document Database
- c) Key-Value Store
- d) Graph Database
Answer: B - MongoDB is a NoSQL document database that stores data in flexible JSON-like documents.
2. What is the default port for MongoDB?
- a) 27017
- b) 3306
- c) 5432
- d) 8080
Answer: A - MongoDB's default port is 27017.
3. Which command shows all databases in MongoDB?
- a) show dbs
- b) show databases
- c) db.listDatabases()
- d) Both A and B
Answer: D - Both
show dbs and show databases display all databases.
4. What is the format of data storage in MongoDB?
- a) XML
- b) CSV
- c) BSON
- d) YAML
Answer: C - MongoDB stores data in BSON (Binary JSON) format.
5. Which operator is used to update existing fields in MongoDB?
- a) $inc
- b) $set
- c) $push
- d) $addToSet
Answer: B -
$set updates the value of a field.
6. What is the primary key in MongoDB called?
- a) _id
- b) primaryKey
- c) key
- d) id
Answer: A - MongoDB automatically creates a unique
_id field as primary key.
7. Which method inserts multiple documents in MongoDB?
- a) insertOne()
- b) insertMany()
- c) addDocuments()
- d) create()
Answer: B -
insertMany() inserts multiple documents at once.
8. What does the $lookup operator do?
- a) Performs a left outer join
- b) Filters documents
- c) Sorts results
- d) Groups documents
Answer: A -
$lookup performs a left outer join between collections.
9. Which command starts the MongoDB shell?
- a) mongod
- b) mongo
- c) mongos
- d) start-mongo
Answer: B - The
mongo command starts the MongoDB shell.
10. What is sharding in MongoDB?
- a) Horizontal partitioning of data
- b) Vertical partitioning of data
- c) Data encryption
- d) Data compression
Answer: A - Sharding distributes data across multiple machines (horizontal scaling).
11. Which index type ensures field values are unique?
- a) Single Field Index
- b) Compound Index
- c) Unique Index
- d) Text Index
Answer: C - Unique indexes reject duplicate values for the indexed field.
12. What is the purpose of the $group stage in aggregation?
- a) Groups documents by specified expression
- b) Filters documents
- c) Sorts documents
- d) Limits documents
Answer: A -
$group groups input documents by specified identifier.
13. Which method removes a document in MongoDB?
- a) deleteOne()
- b) remove()
- c) drop()
- d) Both A and B
Answer: D - Both
deleteOne() and remove() can delete documents (though remove() is deprecated).
14. What is a replica set in MongoDB?
- a) A group of mongod instances with the same data
- b) A backup solution
- c) A type of index
- d) A query optimization technique
Answer: A - A replica set maintains multiple copies of data for high availability.
15. Which operator checks if a field exists?
- a) $exists
- b) $has
- c) $contains
- d) $present
Answer: A -
{ field: { $exists: true } } matches documents where the field exists.
16. What is the purpose of the $match stage in aggregation?
- a) Filters documents
- b) Groups documents
- c) Sorts documents
- d) Projects fields
Answer: A -
$match filters documents like the find() method.
17. Which command creates an index in MongoDB?
- a) db.collection.createIndex()
- b) db.collection.addIndex()
- c) db.collection.makeIndex()
- d) db.collection.buildIndex()
Answer: A -
createIndex() creates indexes to improve query performance.
18. What does the $in operator do?
- a) Matches any value in an array
- b) Checks for null values
- c) Performs logical AND
- d) Performs text search
Answer: A -
{ field: { $in: [value1, value2] } } matches documents where field equals any value in the array.
19. Which method returns a cursor in MongoDB?
- a) find()
- b) findOne()
- c) get()
- d) fetch()
Answer: A -
find() returns a cursor to iterate through results.
20. What is the purpose of the explain() method?
- a) Analyzes query performance
- b) Shows query results
- c) Validates documents
- d) Creates backups
Answer: A -
explain() provides information on query execution plans.