MongoDB Interview Questions&Answers 2

 What are NoSQL databases? What are the different types of NoSQL databases?

A NoSQL database provides a mechanism for storage and retrieval of data that is not based on RDBMS.

Types of NoSQL databases:

1. Document Oriented
2. Key Value
3. Graph
4. Column Oriented

What kind of NoSQL database MongoDB is?

MongoDB is a document oriented database. It stores data in the form of BSON structure based documents. These documents are stored in a collection.

What is a Namespace in MongoDB?

A Namespace is the concatenation of the database name and collection name. For e.g. school.students with school as the database and students as the collection

Compare SQL databases and MongoDB at a high level.

SQL databases store data in form of tables, rows, columns and records. This data is stored in a pre-defined data model which is not very much flexible for today's real-world highly growing applications. MongoDB in contrast uses a flexible structure which can be easily modified and extended.

How is MongoDB better than other SQL databases?

MongoDB allows a highly flexible and scalable document structure. For e.g. one data document in MongoDB can have five columns and the other one in the same collection can have ten columns. Also, MongoDB database are faster as compared to SQL databases due to efficient indexing and storage techniques.

Does MongoDB support foreign key constraints?

No. MongoDB does not support such relationships.

Does MongoDB support ACID transaction management and locking functionalities?

No. MongoDB does not support default multi-document ACID transactions. However, MongoDB provides atomic operation on a single document.

How can you achieve primary key - foreign key relationships in MongoDB?

By default MongoDB does not support such primary key - foreign key relationships. However, we can achieve this concept by embedding one document inside another. Foe e.g. an address document can be embedded inside customer document.

If you remove a document from database, does MongoDB remove it from disk?

Yes. Removing a document from database removes it from disk too.

Mention the command to insert a document in a database called school and collection called persons.

use school;

db.persons.insert( { name: "kadhir", dept: "CSE" } )

What are Indexes in MongoDB?

Indexes support the efficient execution of queries in MongoDB. Without indexes, MongoDB must perform a collection scan, i.e. scan every document in a collection, to select those documents that match the query statement. If an appropriate index exists for a query, MongoDB can use the index to limit the number of documents it must inspect.

How many indexes does MongoDB create by default for a new collection?

By default, MongoDB created the _id collection for every collection.

Can you create an index on an array field in MongoDB? If yes, what happens in this case?

Yes. An array field can be indexed in MongoDB. In this case, MongoDB would index each value of the array.

Does MongoDB provide a facility to do text searches? How?

Yes. MongoDB supports creating text indexes to support text search inside string content. This was a new feature which can introduced in version 2.6.

Mention the command to list all the indexes on a particular collection.

db.collection.getIndexes()

How can you achieve transaction and locking in MongoDB?

To achieve concepts of transaction and locking in MongoDB, we can use the nesting of documents, also called embedded documents. MongoDB supports atomic operations within a single document.

What is Sharding in MongoDB? Explain.

Sharding is a method for storing data across multiple machines. MongoDB uses sharding to support deployments with very large data sets and high throughput operations.

What is Replication in MongoDB? Explain.

Replication is the process of synchronizing data across multiple servers. Replication provides redundancy and increases data availability. With multiple copies of data on different database servers, replication protects a database from the loss of a single server. Replication also allows you to recover from hardware failure and service interruptions.

What is a Storage Engine in MongoDB

A storage engine is the part of a database that is responsible for managing how data is stored on disk. For example, one storage engine might offer better performance for read-heavy workloads, and another might support a higher-throughput for write operations.

Which are the two storage engines used by MongoDB?

MongoDB uses MMAPv1 and WiredTiger.

Refrence: https://www.tutorialspoint.com/