Column and Row-Oriented Databases Overview

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Questions and Answers

What is the purpose of hinted handoff in Cassandra?

To forward write requests to unavailable nodes. (correct)
To establish connections between clusters.
To prioritize read operations for speed.
To permanently delete data from a node.

Which scenario is most suitable for using column-oriented databases like Cassandra?

Systems with high read and low write operations.
Social networking applications requiring write-intensive operations. (correct)
Applications that need immediate data retrieval across all nodes.
Applications needing complex joins between tables.

Which feature is unique to Cassandra's architecture?

Centralized data storage model.
Strict requirement for data normalization.
Peer-to-peer architecture with hinted handoff. (correct)
Automatic sharding of database tables.

What is a limitation of Cassandra Query Language (CQL)?

It lacks support for GROUP and JOIN operations. (B) Signup and view all the answers

What characteristic of Cassandra enables multi data center deployment?

Multi data center replication capability. (D) Signup and view all the answers

What is the primary function of a row key in Cassandra?

To uniquely identify a row and influence data storage order (C) Signup and view all the answers

Which partitioner does Cassandra use by default for data distribution?

Random partitioner (C) Signup and view all the answers

How are columns in Cassandra uniquely identified?

By the column name and a timestamp or version stamp (D) Signup and view all the answers

What do column families in Cassandra resemble in relational databases?

Tables (B) Signup and view all the answers

What is one of the main features of Apache Cassandra?

It is a decentralized database with identical nodes. (B) Signup and view all the answers

Which of the following correctly describes the scalability of Cassandra?

Throughput increases linearly with the addition of new machines. (D) Signup and view all the answers

What type of database is Apache Cassandra classified as?

Wide-column store database (C) Signup and view all the answers

Which statement about the origin of Apache Cassandra is true?

It was created by Facebook to resolve an inbox search issue. (B) Signup and view all the answers

What distinguishes a column-oriented database from a row-oriented database?

All values of a column are stored together on disk. (D) Signup and view all the answers

In a column family, what are super columns primarily used for?

To group together columns that are often read together. (D) Signup and view all the answers

How are rows typically structured in a row-oriented system?

Data is efficiently retrieved for an entire row. (D) Signup and view all the answers

What advantage do column-oriented databases have when dealing with sparse data?

They waste less storage on empty cells. (B) Signup and view all the answers

Which of the following statements best describes column families?

They group super columns together. (A) Signup and view all the answers

When performing a query to find the average score in a column-oriented database, what is the primary requirement?

Accessing only the Score column. (D) Signup and view all the answers

Which characteristic of a column family allows for flexibility in data structure?

Allowing rows to contain varying numbers of columns. (C) Signup and view all the answers

What query type typically performs better in a column-oriented database?

Queries focused on a specific column. (D) Signup and view all the answers

What command would you use to list all available keyspaces in a Cassandra cluster?

DESCRIBE KEYSPACES (C) Signup and view all the answers

Which command allows you to create a new keyspace in Cassandra with specific replication settings?

CREATE KEYSPACE my_keyspace WITH replication = {'class':'SimpleStrategy', 'replication_factor':1} (B) Signup and view all the answers

What command would you use to delete a specific row from a table in Cassandra?

DELETE FROM user WHERE first_name='Bill' (D) Signup and view all the answers

Which command retrieves the description of a specific table in Cassandra?

DESCRIBE TABLE user (C) Signup and view all the answers

To remove all data from a table without removing the table itself, which command should you use?

TRUNCATE user (D) Signup and view all the answers

What is the command to insert a new user named 'Bill Nguyen' into the 'user' table?

INSERT INTO user (first_name, last_name) VALUES ('Bill', 'Nguyen') (B) Signup and view all the answers

Which command would you use to change the keyspace in a Cassandra session?

USE keyspace_name (D) Signup and view all the answers

What does the SELECT COUNT (*) command do in Cassandra?

Counts the total number of rows in the user table (D) Signup and view all the answers

What is the purpose of using triple quotes in Python code for Cassandra?

To handle multi-line strings (C) Signup and view all the answers

What does the command 'CREATE TABLE IF NOT EXISTS user' do in Cassandra?

Creates a user table only if it doesn't already exist (A) Signup and view all the answers

Which statement is true when deleting data in Cassandra?

You can delete specific columns from a row without deleting the entire row (A) Signup and view all the answers

In the provided code, what does the command 'TRUNCATE user' accomplish?

Removes all rows from the user table without deleting the table itself (B) Signup and view all the answers

What is the primary key used in the 'user' table creation based on the code provided? session.execute(""" CREATE TABLE IF NOT EXISTS user ( first_name text, last_name text, PRIMARY KEY (first_name) ) """)

first_name (A) Signup and view all the answers

Which command would you use to remove the entire record of a user named 'Bill'?

DELETE FROM user WHERE first_name='Bill' (D) Signup and view all the answers

What is a key feature of Cassandra's architecture mentioned in the content?

Peer-to-peer approach for data management (A) Signup and view all the answers

Which Python command is used to display all records from the 'user' table in the provided code?

session.execute('SELECT * FROM user') (B) Signup and view all the answers

Study Notes

Column-Oriented Databases

In column-oriented databases, values of a column are stored together on the disk.
They efficiently handle queries that require accessing only a single column.
They can effectively handle sparse data with many null values.
Relational databases can be both row-oriented and column-oriented.

Row-Oriented Systems

Row-based systems are optimized to retrieve entire rows efficiently.
They are useful when retrieving information about a specific entity.
Queries like "Find average score" may require reading the whole data.

### Cassandra

An open-source, distributed data storage system.
Offers high availability, scalability, and consistency.
It differs from relational database management systems (RDBMSs) by using a wide-column store approach.
Originated at Facebook to address the challenges of inbox search scaling in 2008.

Cassandra Features

Distributed: Databases can be spread across multiple servers for scalability.
Decentralized: Every node in the cluster is identical, without a single point of failure.
Elastically Scalable: Read and write throughput increases linearly as new machines are added, with no downtime.

Cassandra Write Operations

If a node is unavailable, other nodes can receive write requests and forward them.
This mechanism is known as "Hinted Handoff".
Nodes store "hints" to send the data to the intended node when it becomes available.

When to Use Column-Oriented Databases

They are suitable for large-scale deployments with a high number of servers or multi-data center availability.
Cassandra supports multi data center deployment with replication for high availability.
Column-oriented databases are beneficial for write-intensive operations, often found in social networking apps.

Cassandra Query Language (CQL)

A simple language for manipulating data stored in Cassandra.
Similar in syntax to SQL.
Limited support for GROUP, JOIN, and ORDER BY operations compared to SQL.

Cassandra Shell

DESCRIBE CLUSTER: Provides information about the current cluster.
DESCRIBE KEYSPACES: Lists all available keyspaces in the cluster.
**USE <keyspace_name>: **Switches to a specific keyspace.
**DESCRIBE TABLES: ** Displays all tables within the current keyspace.

Creating Tables & Keyspaces

CREATE KEYSPACE my_keyspace: Creates a new keyspace with a specified replication strategy.
CREATE TABLE IF NOT EXISTS user: Creates a table named "user" if it does not already exist.

Data Manipulation Commands

INSERT INTO user: Inserts data into the "user" table.
SELECT * FROM user: Retrieves all data from the "user" table.
SELECT COUNT(*) FROM user: Calculates the number of rows in the "user" table.
DELETE last_name FROM user: Deletes the "last_name" column for a specific user.
DELETE FROM user: Deletes an entire row from the "user" table.
TRUNCATE user: Deletes all data within the "user" table.
DROP TABLE user: Removes the table schema from Cassandra.

Cassandra Using Python

Imports the "cassandra.cluster" module to connect to Cassandra.
Uses the "Cluster" class to create a connection to a Cassandra cluster.
Executes CQL statements through the "session" object. Examples include creating keyspaces, defining tables, inserting data, deleting data, and deleting tables.

Key Takeaways

Column-oriented databases are optimized for efficient column retrieval.
Cassandra is a powerful, distributed, NoSQL database for managing large datasets with high availability.
CQL is a query language for interacting with Cassandra that is similar to SQL.
Cassandra offers a Python driver for seamless data access.

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Description

This quiz explores the concepts of column-oriented and row-oriented databases. It highlights the features of Cassandra, a distributed data storage system that utilizes a wide-column store approach. Understand the differences, efficiencies, and applications of each type of database.