Types of databases (relational, NoSQL, object-oriented) in DBMS Theory - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Identify the database type from description

Which type of database stores data in tables with rows and columns and uses SQL for queries?

A Relational database

B NoSQL database

C Object-oriented database

D Graph database

💡 Hint

Think about databases that organize data in rows and columns.

Relational databases organize data in tables with rows and columns and use SQL to query data.

❓ query_result

intermediate

Output of NoSQL document query

Given a NoSQL document database with a collection of user documents, what is the output of this query?

db.users.find({"age": {"$gt": 30}})

Assuming the collection has three users aged 25, 35, and 40.

A Returns users aged 35 and 40

B Returns users aged 25 only

C Returns no users

D Returns users aged 25, 35, and 40

💡 Hint

The query filters users older than 30.

The query finds users with age greater than 30, so it returns users aged 35 and 40.

📋 Factual

advanced

Identify the correct object-oriented database query syntax

Which of the following is a valid way to query objects in an object-oriented database?

A db.objects.find({type: 'Car'})

B objects->filter(type == 'Car')

C SELECT * FROM objects WHERE objectType = 'Car'

D GET /objects?filter=type:Car

💡 Hint

Object-oriented databases often use method calls on objects.

Option B uses a method call style typical for object-oriented databases to filter objects.

❓ optimization

advanced

Best database type for hierarchical data

You need to store and query hierarchical data like organizational charts efficiently. Which database type is best suited?

A Relational database with JOINs

B NoSQL document database

C Object-oriented database

D Graph database

💡 Hint

Think about databases designed for relationships and connections.

Graph databases are optimized for hierarchical and relationship data, making queries efficient.

🔍 Analysis

expert

Why does this NoSQL query fail?

Consider this NoSQL query:

db.products.find({price: {$lt: '100'}})

It returns no results even though products with price less than 100 exist as numbers. Why?

A The $lt operator is invalid in NoSQL queries

B The collection name 'products' is incorrect

C The query uses a string '100' instead of a number 100

D No products have a price field

💡 Hint

Check the data types used in the query condition.

The query compares price to a string '100' but prices are stored as numbers, so no match occurs.