Database Programming Quiz

Question 1: SQLite3 Connection

Which method is used to create a new SQLite3 database connection in Ruby?

SQLite3.new('database.db') SQLite3::Database.new('database.db') SQLite3.connect('database.db') SQLite3::Connection.new('database.db')

Correct Answer: B
SQLite3::Database.new('database.db') is the correct way to create a new SQLite3 database connection. This creates a new Database object that represents the connection to the SQLite file.

Question 2: Prepared Statements

What is the main benefit of using prepared statements in database programming?

They make queries run faster by using indexes automatically They prevent SQL injection attacks and improve performance for repeated queries They automatically create database backups They enable automatic connection pooling

Question 3: PostgreSQL Connection

Which gem is commonly used to connect to PostgreSQL databases in Ruby?

postgresql pg postgres pgsql

Correct Answer: B
The pg gem is the standard Ruby interface for PostgreSQL databases. It provides comprehensive access to PostgreSQL features and is actively maintained.

Question 4: MySQL Connection

What is the recommended gem for connecting to MySQL databases in Ruby?

mysql mysql2 ruby-mysql mysqlclient

Correct Answer: B
mysql2 is the recommended gem for MySQL connections. It's faster and more feature-complete than the older mysql gem, providing better performance and Unicode support.

Question 5: Sequel ORM Datasets

In Sequel ORM, how do you chain conditions to filter records?

DB[:users].filter(active: true).filter(age: 25) DB[:users].where(active: true).where(age: 25) DB[:users].select(active: true).select(age: 25) DB[:users].find(active: true).find(age: 25)

Correct Answer: B
In Sequel, .where() is used to filter records. You can chain multiple .where() calls to add additional conditions, which are combined with AND logic.

Question 6: Transaction Management

What happens when an exception is raised inside a database transaction block?

The transaction is automatically committed The transaction is automatically rolled back The transaction remains open The database connection is closed

Question 7: SQL Injection Prevention

Which of the following is the safest way to include user input in SQL queries?

"SELECT * FROM users WHERE name = '#{user_input}'" "SELECT * FROM users WHERE name = ?" + [user_input] db.execute("SELECT * FROM users WHERE name = ?", [user_input]) "SELECT * FROM users WHERE name = " + user_input

Correct Answer: C
Using parameterized queries with db.execute("SQL", [params]) is the safest approach. The database engine handles escaping and prevents SQL injection attacks by separating the SQL structure from the data.

Question 8: Sequel Associations

In Sequel models, which association type represents a "belongs to" relationship?

one_to_many many_to_one one_to_one many_to_many

Correct Answer: B
many_to_one represents a "belongs to" relationship in Sequel. For example, if a Post belongs to a User, you would use many_to_one :user in the Post model.

Question 9: Connection Pooling

What is the primary benefit of using connection pooling in database applications?

It automatically optimizes SQL queries It improves performance by reusing database connections It provides automatic failover to backup databases It enables automatic schema migrations

Question 10: Raw SQL vs ORM

When might you choose raw SQL over an ORM like Sequel?

For simple CRUD operations on single tables For complex queries, performance optimization, or database-specific features When you want automatic validations and associations For better security against SQL injection

Question 11: Database Migrations

What is the primary purpose of database migrations?

To backup database data To manage schema changes over time in a versioned way To improve query performance To compress database files

Question 12: Sequel Dataset Operations

What does the following Sequel code do: DB[:users].where(age: 25..35).order(:name).limit(10)?

Finds exactly 10 users with age 25 to 35, ordered by name Creates a dataset that will return up to 10 users aged 25-35, ordered by name Updates 10 users to have ages between 25 and 35 Deletes users with age between 25 and 35, keeping only 10

Correct Answer: B
This creates a dataset (lazy query object) that, when executed, will return up to 10 users whose age is between 25 and 35 (inclusive), ordered alphabetically by name. The query isn't executed until you iterate over it or call a method like .all.

Ruby Language

Rails Framework

Production Ready