NoSQL and alternative models in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this MongoDB query?

Consider a MongoDB collection named books with documents containing title and year. What does this query return?

db.books.find({ year: { $gt: 2000 } }, { title: 1, _id: 0 })

Intro to Computing

db.books.find({ year: { $gt: 2000 } }, { title: 1, _id: 0 })

A All book titles published after the year 2000, including their _id

B All books published before the year 2000, including their _id

C All book titles published after the year 2000, without the _id field

D All books published after the year 2000, with all fields

💡 Hint

Look at the filter and projection parts of the query separately.

The filter { year: { $gt: 2000 } } selects books with year greater than 2000. The projection { title: 1, _id: 0 } includes only the title field and excludes the _id field from the output.

🧠 Conceptual

intermediate

Which NoSQL model is best for storing hierarchical data?

You want to store data that naturally forms a tree structure, like categories and subcategories. Which NoSQL database model fits this use case best?

A Document store (e.g., MongoDB)

B Key-value store (e.g., Redis)

C Graph database (e.g., Neo4j)

D Wide-column store (e.g., Cassandra)

💡 Hint

Think about which model can store nested objects easily.

Document stores allow nested documents, making them ideal for hierarchical data like trees.

📋 Factual

advanced

Identify the syntax error in this Cassandra CQL query

Which option contains a syntax error when creating a table in Cassandra?

Intro to Computing

CREATE TABLE users (id UUID PRIMARY KEY, name text, age int);

A CREATE TABLE users (id UUID, name text, age int PRIMARY KEY);

B CREATE TABLE users id UUID PRIMARY KEY, name text, age int;

C CREATE TABLE users (id UUID PRIMARY KEY, name text, age int);

D CREATE TABLE users (id UUID PRIMARY KEY, name text, age int PRIMARY);

💡 Hint

Check the parentheses and keyword placement.

Option B is missing parentheses around the column definitions, which is required syntax in CQL.

❓ optimization

advanced

How to optimize a graph database query for shortest path?

You have a graph database with millions of nodes. You want to find the shortest path between two nodes efficiently. Which approach improves query performance?

A Store the graph as a document store for faster access

B Avoid using indexes to speed up traversal

C Increase the number of edges per node to reduce hops

D Use an index on node properties involved in the query

💡 Hint

Indexes help databases find data faster.

Indexes on node properties help the database quickly locate start and end nodes, improving shortest path query speed.

🔍 Analysis

expert

Why does this Redis command fail with an error?

You run this Redis command:

HSET user:100 name "Alice" age 30

But it returns an error. What is the cause?

A The command syntax requires field-value pairs, but age and 30 are not paired correctly

B The key name cannot contain a colon ':'

C Redis does not support hash data types

D The age value should be a string, not a number

💡 Hint

Check how field-value pairs are passed in HSET.

HSET expects pairs of field and value. The command is correct as shown, so the error must be due to missing quotes or incorrect pairing in the actual command usage.