Best Data Warehousing Multiple Choice Questions (MCQ) to Test Your Knowledge

Data Warehousing: Understanding the Basics


The term "data warehouse" was first coined by Bill Inmon Alin in 1990. According to him, a data warehouse is a subject-oriented, integrated, time-variant, and non-volatile collection of data that is kept separate from an organization's operational database. It can be considered as a more extensive form of DBMS data. In this article, we will discuss the characteristics of a data warehouse, the KDD process, data cleaning, data integration, data selection, data transformation, and the types of data objects and attributes.

Key Points

  • There is no requirement for frequent updating of data on the warehouse.
  • Data in a warehouse helps analysts to make informed decisions in an organization.
  • Data warehouses provide generalized and combined data in a multidimensional view.
  • Data warehouses also provide us with online analytical processing (OLAP) tools which help in interactive and effective analysis.

Characteristics of Data Warehouse

  • Subject-oriented
  • Non-volatile
  • Integrated
  • Time variant

KDD Process

  • KDD stands for Knowledge Discovery from Data.
  • KDD refers to the overall process of discovering useful knowledge from data.

Data Cleaning

Data cleaning is defined as the removal of noisy and irrelevant data from the collection.

  • Cleaning missing values
  • Cleaning noisy data

Data Integration

Data integration is defined as the heterogeneous data from multiple sources combined into a common source.

Data Selection

Data selection is defined as the process where data relevant to the analysis is decided and retrieved from the data warehouse.

Data Transformation

Transformation is defined as the process of transforming data into the appropriate required form required by the mining procedure.

Data Objects and Attributes Types

  • Data sets are made up of data objects.
  • A data object represents an entity.
  • Data objects are described by attributes in the database.


Attributes are data fields that represent a characteristic or feature of a data object.

Types of Attributes

  • Nominal attributes:
    • Relating to names
    • Each value represents some kind of category, code, or state.
    • Also referred to as categorical attributes.
  • Binary attributes:
    • Nominal attributes with only two categories of state(0 and 1).

Defining Datamarts in Data Warehousing

In data warehousing, datamarts refer to a subgroup of the data warehouses. These are smaller, more focused data repositories that contain specific types of data. While data warehouses often contain a broad range of data related to an organization's operations, datamarts are designed to support more specific functions such as sales analysis, marketing campaigns, or financial reporting.

// Example code for implementing a datamart in a data warehouse
CREATE TABLE sales_datamart
  sale_id INT,
  product_id INT,
  customer_id INT,
  sale_date DATE,
  sale_amount DECIMAL(10,2)

The code above creates a "sales_datamart" table within a data warehouse. This table is designed to store data related to sales transactions, including information such as the sale ID, product ID, customer ID, sale date, and sale amount. By structuring data in this way, analysts can more easily access and analyze specific sets of data that are relevant to their work.

Clarifying the Updating of Data Warehouse


Generally, data warehouses are not updated in real-time. Instead, they are updated in batches, either on a daily, weekly, or monthly basis. This makes it easier for analysts to perform complex queries and generate reports without being hindered by the constant influx of data. Real-time data integration tools can be used to facilitate near real-time updates, but this is not the norm for most data warehouses.

// No code to optimize and rephrase

Options in a Data Warehouse

A data warehouse can include the following options:

- Database tables
- Online data
- Flat files

Therefore, the correct answer is option D) All of the above.

System of Data Warehousing for Reporting and Data Analysis

In data warehousing, the most commonly used system is for reporting and data analysis. The purpose of this system is to provide insights into the data that is stored within the warehouse.

Data mining and data storage are also important aspects of data warehousing, but they are not the primary function of the system. Data mining is a process of discovering patterns in large datasets, while data storage is the physical location where the data is stored.

Data integration is the process of combining data from multiple sources into a single, unified view. This is important in data warehousing because it allows for easier data analysis.

Data cleaning is the process of identifying and removing errors and inconsistencies from a dataset. This is also an important aspect of data warehousing because it ensures that the data is accurate and reliable.

Overall, the system of data warehousing is designed to provide a comprehensive view of an organization's data, which can be used for reporting, analysis, and other important business functions.

Usage of Data Warehousing

Data warehousing is primarily used in Decision Support Systems.

The purpose of a data warehouse is to provide a centralized and integrated repository of data that is structured in such a way as to facilitate the efficient querying, reporting and analysis of the information contained within it, using tools such as Data Mining, Online Analytical Processing (OLAP) and other Business Intelligence applications.

Data Warehousing: Small units holding data in a data warehouse

In Data Warehousing, small logical units that hold large amounts of data are known as data marts.

let dataMarts = ["Sales Data Mart", "Marketing Data Mart", "Finance Data Mart", "HR Data Mart"];

These data marts are designed to serve specific business functions and are optimized to provide relevant data to users quickly and efficiently.

Incorrect Property of a Data Warehouse

The incorrect property of a data warehouse is:

 D) Volatile 

The other properties of a data warehouse are:

  • Collection from heterogeneous sources
  • Subject oriented
  • Time variant

Operations that can be performed on a Data Warehouse

One of the operations that can be performed on a data warehouse is the scan operation. This operation allows for the retrieval of data from the warehouse in an efficient manner.

Other operations that can be performed on a data warehouse include:

  • Aggregation
  • Filtering
  • Joining tables
  • Sorting
  • Grouping

Understanding the basis of a data warehouse

In a data warehouse, data is organized and stored in a specific way to allow for efficient querying and analysis. The basis of a data warehouse is a multidimensional model, which allows for the representation of data as facts (measurements or metrics) and dimensions (characteristics describing the facts).

// Sample code for creating a multidimensional model in a data warehouse
CREATE TABLE fact_sales (
  date DATE,
  product_id INT,
  store_id INT,
  sales_amount DECIMAL(10,2)

CREATE TABLE dim_product (
  product_id INT PRIMARY KEY,
  product_name VARCHAR(50),
  category_name VARCHAR(50),
  brand_name VARCHAR(50),

CREATE TABLE dim_store (
  store_id INT PRIMARY KEY,
  store_name VARCHAR(50),
  city VARCHAR(50),
  state VARCHAR(2),

// Additional fact and dimension tables can be added as needed

In this example code, a fact table called "fact_sales" contains sales data that can be analyzed across different dimensions such as "dim_product" and "dim_store". The dimension tables provide additional information about the products and stores, which can be used to filter and group the sales data.

Identifying the Multidimensional Model of a Data Warehouse

When referring to the multidimensional model of a data warehouse, the correct term to use is a "data cube".

// Example usage of a data cube variable
var myDataCube = new DataCube();

Understanding DSS in a Data Warehouse

In a data warehouse, DSS stands for Decision Support System. It is a computer-based system that helps users to make decisions based on data analysis and data mining. DSS aids decision-makers in gathering and interpreting large amounts of data from multiple sources and applying analysis techniques to generate meaningful insights that can inform business decisions.

// This code demonstrates the implementation of a Decision Support System for a sales department

public class SalesDSS {
    private SalesData salesData;
    private CustomerData customerData;
    public SalesDSS() {
        salesData = new SalesData();
        customerData = new CustomerData();
    public void generateSalesReport(Date startDate, Date endDate) {
        List<Sale> sales = salesData.getSalesBetweenDates(startDate, endDate);
        Map<String, Integer> salesByProduct = new HashMap<>();
        Map<String, Integer> salesByCustomer = new HashMap<>();
        for (Sale sale : sales) {
            String productName = sale.getProductName();
            String customerName = customerData.getCustomerById(sale.getCustomerId()).getName();
            salesByProduct.put(productName, salesByProduct.getOrDefault(productName, 0) + sale.getQuantity());
            salesByCustomer.put(customerName, salesByCustomer.getOrDefault(customerName, 0) + sale.getQuantity());
        System.out.println("Sales Report from " + startDate.toString() + " to " + endDate.toString());
        System.out.println("Sales by Product:");
        for (String productName : salesByProduct.keySet()) {
            System.out.println(productName + ": " + salesByProduct.get(productName));
        System.out.println("Sales by Customer:");
        for (String customerName : salesByCustomer.keySet()) {
            System.out.println(customerName + ": " + salesByCustomer.get(customerName));
    // other DSS methods...

Understanding the Time Horizon in Data Warehousing

In data warehousing, the time horizon refers to the period of time for which historical data is stored in the data warehouse. It is important to choose the appropriate time horizon to ensure that the data warehouse provides accurate, relevant and useful information for decision-making purposes.

The ideal time horizon for a data warehouse is typically between 5-10 years, as this allows organizations to analyze long-term trends and make informed decisions based on historical data. However, the time horizon may vary based on the business requirements, industry standards, regulatory compliance and other factors.

It is also important to periodically review and update the time horizon in the data warehouse to ensure that it aligns with the changing business needs and objectives.

Where can data be updated?

The data can be updated in the operational environment.

// Example code for updating data in operational environment
public void updateDataInOperationalEnvironment(Data data) {
     // code implementation for updating data in operational environment

The above code shows a method that can be used to update data in the operational environment. The "Data" parameter represents the data that needs to be updated.

It is important to note that updating data in the operational environment requires careful planning and proper implementation to ensure that the data is updated accurately and without causing any disruptions to any ongoing processes.

Identifying the source of data warehouse data

In the context of data warehousing, the source of all data stored in a data warehouse is referred to as the operational environment. It is the environment where the data is generated by various operational systems such as transactional databases, ERP systems, CRM systems, etc. Data is extracted from these systems, preprocessed and then transformed before loading it into the data warehouse.

The operational environment is the core component of any data warehousing architecture, and it plays a crucial role in determining the quality of data that is stored in a data warehouse.

Identifying the most common source of change data in refreshing a data warehouse

In order to refresh a data warehouse, it is important to identify the most common source of change data. The answer is Queryable change data, which is the data that can be easily queried and it can be accessed by the data warehouse through a query. This is the most common source of change data.

Logged change data, on the other hand, refers to changes that are logged as they occur. Cooperative change data refers to changes that are shared in a cooperative manner among data sources. Snapshot change data refers to data that is captured at a specific point in time.

Therefore, Queryable change data is the most frequently used source of change data for data warehouses.

Responsibility for Querying and Reporting Against Data Warehouse Tables

In a data warehouse environment, end-users are typically responsible for running queries and generating reports against the data warehouse tables.

Software, hardware, and middleware are all important components of a data warehouse system, but they are not directly responsible for running queries and reports. Instead, these components work together to provide a platform for end-users to access and analyze the data in the warehouse.

Approaches for Integrating Heterogeneous Databases in Data Warehousing

There are two main approaches for integrating heterogeneous databases in data warehousing, which are:

1) Query driver approach

This approach involves the use of a middleware layer that sits between the user and the various data sources. When a user queries the data warehouse, the middleware generates SQL queries that are sent to the appropriate data sources. The results are then combined by the middleware and presented to the user as a single result set.

2) Update-driven approach

This approach involves the replication of data from the heterogeneous databases into a centralized hub. This hub is then used to populate the data warehouse. The replication can be done in real-time or in batches, and can be triggered by changes to the source data or on a schedule.

Both approaches have their pros and cons, and the choice between them will depend on the specific requirements of the data warehousing project.

Source of Classification Rules

In the context of decision-making processes, classification rules are derived from a decision tree.

A decision tree is a graphical representation of possible decisions and their consequences or potential outcomes. It is made up of nodes, branches, and leaves. Decision rules are extracted from the tree's nodes, which indicate the conditions necessary to lead to a certain branch or outcome.

Therefore, the correct answer is B) Decision tree.

// No code provided for this question

Correcting Information on Surrogate Keys

In data modeling, a surrogate key is a unique identifier that is added to a table to serve as its primary key. It is not a primary key of a fact table but a simple integer value or a list of running numbers generated by the database management system (DBMS).

When using a surrogate key, it is usually a good practice to make it the primary join key between the fact and dimension tables. This will enable efficient querying and provide an optimal performance of the data warehouse.

Identifying Fragmented and Inconsistent Data in Operational Systems

In operational systems, it is common for data to be fragmented and inconsistent, which means that True is the correct answer.

//Code example not applicable for this text-based task

Specialized Data Warehouse Databases

In the realm of data warehousing, a specialized database is always required to hold large amounts of data. Among the four options, Redbrick is the specialized data warehouse database.

Identifying the Correct Database Architecture

The correct option for the database architecture on which the database system is based depends on the technology used to create the architecture. Out of the given options, the right choice is B) RDBMS.

RDBMS stands for relational database management system. As the name suggests, this architecture manages data in a relational manner, using tables to store and organize information. SQL Server and Sybase are specific examples of RDBMS technologies, while DBMS is a more general term for any database management system, which can include RDBMS and other architectures. Therefore, the answer to this question is B) RDBMS.

//No code provided for this question

Determining the Percentage of Data Redundancy between Environments

Can you provide information on the percentage of data redundancy between environments?

Clustering Methods

In clustering analysis, we group data points with similar characteristics into clusters. We can use different algorithms to do this.

Out of the following four methods, K nearest neighbor method is not a clustering method.

  • K nearest neighbor method
  • K mean method
  • Self-organizing feature map method
  • Agglomerative method

// Here is an example of Kmeans Clustering in Python
from sklearn.cluster import KMeans
import pandas as pd

# load data
data = pd.read_csv('data.csv')

# create KMeans object with 3 clusters
kmeans = KMeans(n_clusters=3, random_state=0)

# fit Kmeans object to data

# get labels for all points
labels = kmeans.labels_

# get centroids of clusters
centroids = kmeans.cluster_centers_

What is ETL?

ETL stands for Extract, Transform, and Load. It refers to the process of extracting data from various sources, transforming it into a format that can be easily analyzed or used for specific purposes, and loading it into a target database or data warehouse.

The Extract phase involves extracting data from various sources such as databases, spreadsheets, and APIs. Then the data undergoes the Transform phase, where it goes through cleaning, validation, and transformation to match the requirements of the target database. Finally, the processed data is loaded into the target database during the Load phase.

ETL is a crucial part of data integration, business intelligence, and data warehousing. It helps organizations to maximize the value of their data by making it easily accessible, understandable, and usable.

What Does ETL Stand For?

ETL stands for Extract, Transform, and Load.

Components of an Active Data Warehouse Architecture

The active data warehouse architecture includes all of the following components:

  1. Near real-time updates
  2. Data extraction from various internal and external sources
  3. At least one data mart

Therefore, the correct answer is D) all of the above are included in an active data warehouse.

// No code to show as this is a general information text

Relationship Types in a Star Schema

In a star schema, the relationship between the fact table and dimension tables is one to many. This means that a single fact in the fact table can be associated with multiple dimensions in the dimension table. The relationship is established through a common key column in both the fact and dimension table. The fact table stores the measures and metrics while the dimension tables store the descriptive information about the measures. Understanding the relationship types is crucial while designing and querying data in a star schema.

Null Values in Programming

In programming, a null value is used to indicate the absence of a value. It does not represent a numeric value with a value of 0. The concept of a null value is used to indicate that a variable or expression does not have a value, which can occur in situations like uninitialized variables, missing data, or when a value cannot be assigned for some reason. Checking for null values is an important part of error handling and ensures that the program does not crash unexpectedly.

// Example of a null value check in Java
Integer num = null; // initialize variable with null value
if(num == null) {
   System.out.println("Value is null"); // output message if value is null

Importance of Data Cleaning

Data cleaning is essential in data mining as it aims to improve the quality of data by removing any unnecessary or irrelevant elements, such as duplicates or inconsistencies. The main uses of data cleaning include:

  • Removing noisy data
  • Transforming incorrect data into correct data
  • Correcting inconsistencies in data

All of the above help to ensure that data is accurate, reliable and consistent, which in turn helps to improve the quality of insights and decisions that are made based on the data. Therefore, it is crucial to perform data cleaning as part of the data mining process.


# Example code for data cleaning
import pandas as pd

# Load data into a dataframe
df = pd.read_csv('data.csv')

# Remove duplicates

# Remove null values 

# Correct any misspelled or incorrect entries 
df['name'].replace({'jonh': 'john', 'stevee': 'steve'}, inplace=True)

# Save cleaned data to a new csv file 
df.to_csv('cleaned_data.csv', index=False)

Technology Suited for Data Mining

Out of the following technologies mentioned, the technology not well suited for data mining is one limited to specific data types, such as numeric data types. The other technologies mentioned, including data visualization, expert system technology, and parallel architecture, are well suited for data mining.

// Example of a data mining algorithm using parallel architecture
function parallelDataMining(data) {
  // divide data into chunks
  const chunks = splitDataIntoChunks(data);

  // process each chunk in parallel
  const results = => processDataChunk(chunk));

  // combine results from each chunk
  const combinedResults = combineResults(results);

  return combinedResults;

In this example, we use parallel architecture to divide the data into chunks and process each chunk simultaneously. This results in faster processing and analysis of large datasets, which is a key aspect of data mining. By using a parallel processing algorithm, we can effectively mine data and extract valuable insights to inform our decision making.

Understanding OLTP


stands for Online Transaction Processing. It is a type of real-time transaction processing that involves processing small, frequent transactions in a production environment. This system is commonly used in banking and e-commerce industries where quick transaction processing is essential. In contrast,


(Online Analytical Processing) is used for analyzing large amounts of data and generating reports. It is important to note the difference between these two systems when designing a database.

Understanding Data Warehousing

The correct answer is A) Data warehousing. Data warehousing is a process that involves organizing large amounts of data from different sources to provide meaningful insights for decision making. It is an object-oriented, integrated, time-variant, and nonvolatile collection of data that supports management decisions.

Data mining, web mining, and text mining are related concepts, but they are not synonymous with data warehousing. Data mining refers to the process of extracting information from a dataset and identifying patterns and relationships between variables. Web mining involves extracting information from web data, while text mining involves analyzing unstructured text data.

It's important to understand the differences between these concepts to effectively leverage data for business decision-making.

Where is the Data Stored, Retrieved and Updated?

The data is stored, retrieved, and updated in OLTP.

// Sample code for connecting to a database using OLTP
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DatabaseConnection {
    // URL of the database server
    private static final String url = "jdbc:mysql://localhost:3306/myDatabase";
    // Username for accessing the database   
    private static final String user = "root";
    // Password for accessing the database
    private static final String password = "myPassword";

    public static void main(String[] args) {
        Connection conn = null;
        try {
            // Register JDBC driver

            // Open a connection
            conn = DriverManager.getConnection(url, user, password);

            // Do something with the connection such as execute queries

        } catch (SQLException se) {
            // Handle errors for JDBC
        } catch (Exception e) {
            // Handle errors for Class.forName
        } finally {
            // Close the connection
            try {
                if (conn != null) conn.close();
            } catch (SQLException se) {

Understanding the Heart of a Warehouse

In a warehouse, the data warehouse database servers are considered the heart. These are the servers that store, organize, and manage all the data collected. The data stored in the warehouse is essential for analytical purposes, so it is important that the database servers are reliable, scalable, and secure. Therefore, the data warehouse is an integral part of any business that relies on data-driven decision making.

Pattern Evaluation Issues in Data Mining

In data mining, pattern evaluation issues fall under the category of mining methodology and user interaction. This includes the evaluation of discovered patterns to determine their relevance and usefulness in achieving the desired goals of the data mining process.

Performance issues may also arise during the evaluation process, but they are not directly related to pattern evaluation. The use of diverse data types can affect the evaluation process, but it is not a separate category for pattern evaluation issues.

Therefore, the correct answer is C) Mining methodology and user interaction issue.

Mapping Core Warehouse Metadata to Business Concepts

In a data warehouse, the core metadata needs to be mapped to business concepts that are familiar and useful to end-users. This process is known as metadata mapping.

Out of the given options, the correct answer is B) Application-level metadata. Application-level metadata is responsible for mapping the technical details of the data warehouse to business concepts that can be easily understood by end-users.

Algorithmic level metadata deals with the technical details of the algorithms used in processing data within the warehouse.

Core level metadata comprises of all the basic information required to operate and manage the data warehouse.

Enduser level metadata pertains to the customizations that are made for individual users' needs, such as defining user roles and permissions.

Purpose of a Query Tool

A query tool is designed for the purpose of acquiring data from a database or other sources. It allows users to retrieve data using specific criteria and generate reports based on that data.

Other options listed such as Information delivery, Information exchange, and Communication are not the primary functions of a query tool, but they can be secondary features or benefits that come with using the tool.

What is DMQL?

DMQL stands for Data Mining Query Language. It refers to a query language used for data mining tasks, which allows data analysts and researchers to retrieve information from large datasets. DMQL can be used to filter and manipulate data to extract patterns and trends that can help in making decisions.

Components of Data Mining System Classification

In order to effectively mine data, it is necessary to have a well-structured data mining system classification. Such a system typically comprises three major components:

  1. Machine Learning
  2. Database Technology
  3. Information Science

Each of these components plays a critical role in the data mining process. Machine learning, for example, focuses on developing algorithms that can automatically identify patterns in data. Database technology, on the other hand, is concerned with the management and organization of large amounts of data, while information science focuses on the analysis and interpretation of that data.

By combining these three components, a data mining system can effectively process and extract valuable insights from complex data sets. Therefore, the correct answer to the given question is option D - All of the above.

//Example code demonstrating the use of machine learning, database technology, and information science for data mining

Where are classification rules extracted from?

The classification rules are extracted from a decision tree.

Method of Incremental Conceptual Clustering

The technique of incremental conceptual clustering refers to the process of grouping similar objects together based on certain shared attributes. One of the popular methods of performing incremental conceptual clustering is COBWEB.

COBWEB is a technique that utilizes a hierarchical approach to classify objects into clusters. It begins with the whole dataset and splits it up into smaller clusters based on the shared attributes of the objects.

This process is repeated until no further aggregation of clusters is possible. COBWEB is a probabilistic method that uses statistical methods to determine the closeness of objects based on their attributes.

Other methods of clustering include OLAP, STING, and CORBA, but they are not related to the incremental conceptual clustering technique.

What is a Multidimensional Database?

A multidimensional database, commonly known as a Relational Database Management System (RDBMS), is a database system that allows for multiple dimensions of data to be analyzed and viewed. It is designed to efficiently handle large amounts of data and supports complex queries and data analysis.


The source data from the warehouses comes from ORDBMS (Object-Relational Database Management System).

ORDBMS is a type of database management system that stores data in a way that allows it to be represented as objects in the application code. It combines the features of both the object-oriented and relational database management systems, making it suitable for complex and large datasets.

CRM Technology: Personalization

In the field of CRM, the technology area is commonly referred to as personalization. This involves tailoring the customer experience to meet individual needs and preferences. By using customer data and insights, businesses can deliver more relevant and personalized interactions that improve customer satisfaction, increase loyalty, and drive revenue. Personalization technology includes various techniques like machine learning, predictive modeling, and recommendation engines to analyze customer behavior and provide personalized recommendations and offers. Ultimately, personalization is about building strong, lasting relationships with customers and delivering exceptional experiences that truly resonate with each individual.

MDDB - Multidimensional Database

MDDB stands for Multidimensional Database, which is a type of database that stores data in more than two dimensions, allowing for faster data analysis and queries.

Definition of Reconciled Data

Reconciled data refers to the most recent, accurate and consistent data that serves as the primary source for all decision-making processes within an organization. It is the product of combining and standardizing disparate data sets from various operational systems, ensuring that the information is consistent, up-to-date, and devoid of errors. Businesses use reconciled data as a reference point for decision support, strategic planning and forecasting.

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