L.11

Question 1

What are the two main types of data representation?

Answer 1

Structured and unstructured data.

Question 2

What is semi-structured data?

Answer 2

Data that does not have a strict schema but follows certain rules, like JSON or XML.

Question 3

What are three examples of semi-structured data formats?

Answer 3

XML, JSON, YAML.

Question 4

What is XML primarily used for?

Answer 4

As a markup language for semi-structured data representation.

Question 5

What does a well-formed XML document require?

Answer 5

It must follow all XML syntax rules.

Question 6

How is JSON different from XML?

Answer 6

JSON is a lightweight data-interchange format that is easier to read and write.

Question 7

What are the basic data types in JSON?

Answer 7

Number, String, Boolean, Array, Object, Null.

Question 8

What is NoSQL?

Answer 8

A category of databases designed for semi-structured or unstructured data.

Question 9

What does NoSQL stand for?

Answer 9

“Not Only SQL.”

Question 10

Name four types of NoSQL databases.

Answer 10

Key/Value Stores, Document Stores, Column-Based Stores, Graph Databases.

Question 11

What type of NoSQL database is MongoDB?

Answer 11

Document Store.

Question 12

What command lists all databases in MongoDB?

Answer 12

show dbs

Question 13

What command connects to a specific database in MongoDB?

Answer 13

use <database></database>

Question 14

What is the basic CRUD operation in MongoDB to retrieve documents?

Answer 14

db.<collection>.find()</collection>

Question 15

How do you find all documents in MongoDB where ‘number’ is greater than 28790?

Answer 15

db.issues.find({number: {$gt: 28790}})

Question 16

What operator in MongoDB returns only unique values?

Answer 16

distinct()

Question 17

What does MongoDB’s _id field represent?

Answer 17

A unique identifier for each document.

Question 18

What MongoDB feature is used to join collections?

Answer 18

Aggregation pipeline with $lookup.

Question 19

What is an advantage of NoSQL databases over SQL?

Answer 19

Scalability and handling of unstructured data.

Question 20

What is a disadvantage of NoSQL compared to SQL?

Answer 20

Lack of ACID compliance and complex query languages.

Question 21

What are the three key characteristics of semi-structured data?

Answer 21

• Mixes data and metadata
• Does not have a rigid schema
• Often stored in formats like XML or JSON

Question 22

What is the main advantage of JSON over XML?

Answer 22

JSON is lightweight, easier to read and write, and natively supported in JavaScript.

Question 23

What is serialization in computing?

Answer 23

The process of converting an object or data structure into a format that can be stored or transmitted.

Question 24

How does MongoDB handle 1-to-N relationships?

Answer 24

By embedding related documents as sub-elements.

Question 25

What is an example of a Key/Value store NoSQL database?

Answer 25

Redis or DynamoDB.

Question 26

What is an example of a Graph database?

Answer 26

Neo4j.

Question 27

What is an example of a Column-based NoSQL database?

Answer 27

HBase.

Question 28

What is an example of a Document Store NoSQL database?

Answer 28

MongoDB.

Question 29

How do you retrieve all collections in a MongoDB database?

Answer 29

show collections

Question 30

How do you display all documents in a MongoDB collection?

Answer 30

db..find().pretty()

Question 31

What does the $size operator do in MongoDB?

Answer 31

Filters documents where an array field has a specific number of elements.

Question 32

What does the $set operator do in MongoDB?

Answer 32

Updates specific fields in a document.

Question 33

How do you count documents in a MongoDB collection?

Answer 33

db..count({query})

Question 34

What is an aggregation pipeline in MongoDB?

Answer 34

A framework for data transformation and analysis using multiple stages.

Question 35

How do you exclude the _id field in a MongoDB query result?

Answer 35

db.issues.find({}, { _id: false })

Question 36

What is sharding in NoSQL databases?

Answer 36

A method of distributing data across multiple servers to improve scalability.

Question 37

What are the main trade-offs of NoSQL databases?

Answer 37

They sacrifice strict consistency for scalability and performance.

Question 38

What is query-by-example in MongoDB?

Answer 38

A querying mechanism where users specify example fields and values to match.

Question 39

How do you update a document in MongoDB?

Answer 39

db..update({query}, {$set: {field: value}})

Question 40

What is the role of MongoDB’s $lookup operator?

Answer 40

It allows for performing joins between collections in the aggregation pipeline.

Question 41

What does eventual consistency mean in NoSQL?

Answer 41

Updates to a database may not be immediately reflected across all nodes, but will be consistent over time.

Question 42

Why is MongoDB popular for web applications?

Answer 42

Its flexibility, scalability, and support for JSON-like documents make it ideal for dynamic applications.

Question 43

What is a drawback of using NoSQL over SQL databases?

Answer 43

Complex transactions and consistency guarantees can be harder to manage.

Question 44

What is a collection in MongoDB?

Answer 44

A grouping of MongoDB documents, similar to a table in relational databases.

Question 45

How do you find documents in MongoDB where a field is null?

Answer 45

db..find({ field: null })

Question 46

What is a primary reason to use NoSQL over SQL?

Answer 46

Handling large volumes of unstructured or semi-structured data.

Question 47

How does MongoDB handle schema evolution?

Answer 47

MongoDB is schema-less, meaning documents in a collection do not need to follow a fixed structure.

Question 48

What is the difference between well-formed and valid XML?

Answer 48

Well-formed XML follows syntax rules, while valid XML conforms to a defined schema (DTD).

Question 49

How can you filter MongoDB documents based on a condition inside an array?

Answer 49

Using dot notation, e.g., db.issues.find({"labels.default": true})

Question 50

What is the main takeaway from the lecture on NoSQL?

Answer 50

NoSQL databases provide scalable, flexible solutions for semi-structured and unstructured data.