Q.1 What is the primary purpose of a data warehouse?
To process transactions
To store raw logs
To support decision making
To replace operational databases
Explanation - A data warehouse is designed to provide insights and support strategic decision-making rather than operational tasks.
Correct answer is: To support decision making
Q.2 Which schema uses a central fact table connected to multiple dimension tables?
Snowflake schema
Star schema
Galaxy schema
Network schema
Explanation - In a star schema, the fact table is at the center with dimension tables directly connected, forming a star-like shape.
Correct answer is: Star schema
Q.3 Who is widely recognized as the father of data warehousing?
E.F. Codd
Bill Inmon
Ralph Kimball
Michael Stonebraker
Explanation - Bill Inmon is known as the father of data warehousing for his contributions to the architecture and methodology.
Correct answer is: Bill Inmon
Q.4 Which of the following is NOT a characteristic of a data warehouse?
Subject-oriented
Volatile
Integrated
Time-variant
Explanation - Data warehouses are non-volatile, meaning data is stable and primarily read for analysis.
Correct answer is: Volatile
Q.5 In a data warehouse, ETL stands for?
Extract, Transform, Load
Edit, Transfer, Link
Evaluate, Test, Launch
Extract, Transfer, Learn
Explanation - ETL is the process of extracting data from sources, transforming it into a suitable format, and loading it into the warehouse.
Correct answer is: Extract, Transform, Load
Q.6 What does OLAP stand for?
Online Logical Analytical Processing
Online Analytical Processing
Offline Analytical Processing
Operational Logical Analytical Processing
Explanation - OLAP enables multidimensional analysis of data stored in a warehouse for faster insights.
Correct answer is: Online Analytical Processing
Q.7 Which of the following best describes a data mart?
A small transactional database
Subset of data warehouse focused on specific business area
Collection of operational systems
Raw data staging area
Explanation - Data marts are designed to serve specific departments like sales or marketing with targeted data.
Correct answer is: Subset of data warehouse focused on specific business area
Q.8 Which schema is a normalized form of star schema?
Galaxy schema
Snowflake schema
Bus schema
Fact constellation
Explanation - Snowflake schema normalizes dimensions into multiple related tables for storage efficiency.
Correct answer is: Snowflake schema
Q.9 Which component of data warehouse is responsible for cleaning and transforming data?
Staging area
Metadata repository
Presentation layer
OLAP engine
Explanation - The staging area is where raw data is extracted and transformed before loading into the warehouse.
Correct answer is: Staging area
Q.10 Metadata in data warehousing is best described as?
The actual data values
Data about data
Redundant storage
User queries
Explanation - Metadata provides information about the structure, source, and meaning of data in the warehouse.
Correct answer is: Data about data
Q.11 Which of the following is a bottom-up approach to data warehousing?
Inmon’s approach
Kimball’s approach
Hybrid approach
Star schema
Explanation - Kimball suggests building data marts first, which are later integrated into a warehouse.
Correct answer is: Kimball’s approach
Q.12 What is a fact table?
A table storing business rules
A table storing transactional raw data
A table storing measurements and keys to dimensions
A metadata catalog
Explanation - Fact tables store numeric measures and foreign keys linking to dimension tables.
Correct answer is: A table storing measurements and keys to dimensions
Q.13 Which type of OLAP uses relational databases to store data?
MOLAP
ROLAP
HOLAP
DOLAP
Explanation - ROLAP uses relational databases to support OLAP operations, leveraging SQL queries.
Correct answer is: ROLAP
Q.14 Which one is NOT a layer in data warehouse architecture?
Data source layer
Staging layer
Presentation layer
Transaction processing layer
Explanation - Transaction processing is part of OLTP, not data warehouse design.
Correct answer is: Transaction processing layer
Q.15 A conformed dimension is?
Dimension used in multiple fact tables consistently
Dimension with no hierarchy
Dimension only for one data mart
Dimension automatically generated
Explanation - Conformed dimensions are shared across different fact tables, ensuring uniformity.
Correct answer is: Dimension used in multiple fact tables consistently
Q.16 Which layer provides tools for end-user analysis in a data warehouse?
Staging layer
ETL layer
Presentation layer
Source layer
Explanation - The presentation layer holds the processed data and provides access for analysis tools.
Correct answer is: Presentation layer
Q.17 Which of the following is an advantage of star schema?
Normalization reduces redundancy
Fast query performance
Reduced storage usage
Complex joins supported
Explanation - Star schema’s denormalized design improves query performance by reducing joins.
Correct answer is: Fast query performance
Q.18 What is the role of surrogate keys in a warehouse?
To replace natural keys
To ensure uniqueness across dimensions
To simplify joins
All of the above
Explanation - Surrogate keys replace natural keys, enforce uniqueness, and ease join operations.
Correct answer is: All of the above
Q.19 Which approach integrates multiple data marts into a warehouse?
Top-down
Bottom-up
Hybrid
Snowflake
Explanation - In Kimball’s bottom-up approach, data marts are built first and then combined into a data warehouse.
Correct answer is: Bottom-up
Q.20 Which is the correct sequence in ETL process?
Transform → Extract → Load
Extract → Load → Transform
Extract → Transform → Load
Load → Extract → Transform
Explanation - Data is first extracted, then transformed to match schema, and finally loaded into the warehouse.
Correct answer is: Extract → Transform → Load
Q.21 Which of these best describes slowly changing dimensions (SCD)?
Dimensions that do not change
Dimensions whose values evolve over time
Dimensions with no primary key
Dimensions updated every day
Explanation - SCDs handle how dimension attributes change over time, such as address updates.
Correct answer is: Dimensions whose values evolve over time
Q.22 What is the purpose of a factless fact table?
Stores only dimension keys without measures
Stores textual data only
Stores only metadata
Stores only surrogate keys
Explanation - Factless fact tables record events or coverage with only dimension keys, no numerical facts.
Correct answer is: Stores only dimension keys without measures
Q.23 In a warehouse, data granularity refers to?
Data accuracy
Data detail level
Data redundancy
Data format
Explanation - Granularity defines the level of detail stored, e.g., daily vs monthly sales.
Correct answer is: Data detail level
Q.24 Which one is an example of a dimension attribute?
Total Sales
Customer Name
Profit Margin
Revenue
Explanation - Dimension attributes describe entities, such as customer names, product categories, etc.
Correct answer is: Customer Name
Q.25 A fact constellation schema is also known as?
Galaxy schema
Snowflake schema
Star schema
Cube schema
Explanation - Fact constellation or galaxy schema involves multiple fact tables sharing dimension tables.
Correct answer is: Galaxy schema