Revature MongoDB

Question 1

What does BASE stand for?

Answer 1

Base stands for Basic Availability, Soft-state, Eventual consistency. It describes the fundamental principles of a NoSQL database focusing on scalability, flexibility and high availaility.

Question 2

What is a database in Mongo?

Answer 2

A database in Mongo is a grouping of unstructured data in JSON format

Question 3

What is a collection?

Answer 3

Equates to a table

Question 4

What is a document?

Answer 4

Equates to a row

Question 5

What rules does Mongo enforce about the structure of documents inside a collection?

Answer 5

In Mongo documents are stored in bson (binary json). The document size cannot be over 16mb and each document in a collection must have a _id

Question 6

A distributed data store?

Answer 6

A distributed data store stores data across multiple computers. Data can be partitioned or sharded across multiple nodes to improve load balance, allow for scalability and fault tolerance

Question 7

What is High Availability? How is it achieved in Mongo?

Answer 7

High availability is the ability of a system to operate continuously without failing for a designated period of time. Mongo achieves it through replica sets

Question 8

What is Scalability? How is it achieved in Mongo?

Answer 8

Scalability is the ability of a database to grow in size. It is achieved both vertically and horizontally in MongoDB. Horizontally through sharding and replica sets

Question 9

Explain replica sets

Answer 9

A replica set is a group of MongoDB servers that maintain the same data set to provide high availability and redundancy. It ensures that the system can continue to function even if one or more nodes fail.

Question 10

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

Answer 10

NoSQL is a type of nonrelational database query language; Wide column, document, key-value, graph

Question 11

What kind of NoSQL database MongoDB is?

Answer 11

It is a document database

Question 12

Which are the most important features of MongoDB?

Answer 12

Can handle unstructured data

Question 13

What is a Namespace in MongoDB?

Answer 13

The name of the collection, including the database.

Question 14

Which all languages can be used with MongoDB?

Answer 14

Many popular languanges allow you to interact with MongoDB. Recently we have been using the MongoDB drivers in python to query the database usuing mongoDB query language.

from pymongo import MongoClient

Connect to MongoDB
client = MongoClient(‘mongodb://localhost:27017’)

Select database and collection
db = client[‘myDatabase’]
collection = db[‘myCollection’]

Find all documents
documents = collection.find()
for doc in documents:
print(doc)

Find documents with a specific condition
specific_documents = collection.find({“age”: {“$gt”: 25}})
for doc in specific_documents:
print(doc)

client.close()

Question 15

Compare SQL databases and MongoDB at a high level.

Answer 15

SQL databases are structured while MongoDB is used to save unstructured data

Question 16

How is MongoDB better than other SQL databases?

Answer 16

It is much faster than other SQL databases; Much more scalable; More flexible

Question 17

Does MongoDB support foreign key constraints?

Answer 17

No, this is because it is a noSQL document database that utilizes keys and value pairs

Question 18

Does MongoDB support ACID transaction management and locking functionalities?

Answer 18

Yes it does. This is done through multi document Acid transaction and document level locking.

Question 19

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

Answer 19

By embedding a document inside another

{
“_id”: 1,
“name”: “Order 1”,
“items”: [
{ “product_id”: 101, “quantity”: 2 },
{ “product_id”: 102, “quantity”: 1 }
]
}

Question 20

When should we embed one document within another in MongoDB?

Answer 20

When we want to relate the two documents

Question 21

Mention what is ObjectId composed of?

Answer 21

4-byte timestamp value representing object’s creation; 5-byte random value; 3-byte incrementing counter

Question 22

What is a distributed application

Answer 22

A distributed application is a software application that runs on multiple computers or nodes within a network as a unified system. It allows for fault tolerence, scalability and concurrency