Updated May 12, 2023
Introduction to Data Warehousing Interview Questions and Answers
A data warehouse is a central repository that stores heterogeneous data from various sources. The data in a warehouse can be used for analytical reporting, structured or ad hoc queries, and decision-making. Collecting data from multiple sources and storing it in the central repository is called Data Warehousing.
The data may be of several types, like structured, semi-structured, or unstructured data. The data from various sources is processed, transformed, and ingested into a single database called a data warehouse. Users can access this processed data in the data warehouse through multiple tools like Business Intelligence tools, SQL clients, spreadsheets, etc. This data helps to perform data mining operations that help to find some pattern in the data.
Now, if you are looking for a job related to Data Warehousing, you must prepare for the 2023 Data Warehousing Interview Questions. Every interview is indeed different as per the various job profiles. Here, we have prepared the important Data Warehousing Interview Questions and Answers which will help you get success in your interview.
Now Let us understand some of the critical 2023 Datawarehousing Interview Questions that can be asked in an interview. But this doesn’t mean these are the only questions to be asked in an interview; you must be prepared thoroughly regarding each topic we discuss here. These questions are divided into two parts as follows:
Part 1 – Data Warehousing Interview Questions (Basic)
This first part covers basic Data Warehousing Interview Questions and Answers
Q1. What is Data Warehousing?
Answer:
Data Warehousing is a process of collecting data from various sources, processing it, and storing it in a vast database; thus, the processed data could be used for multiple purposes like analytical reporting, business intelligence or data mining, etc. The basic idea behind the data warehouse is to store vast amounts of data.
Q2. What is the difference between a Database and Data Warehouse?
Answer:
Please find below the different tables that Data Warehousing supports are:
| Database | Data Warehouse |
| Collection of data used for storing, accessing, and retrieval | Collection of data used for performing analytics |
| Constrained with the single application | Multiple applications can use it |
| Stores normalized data | Data need not be normalized; usually stored as denormalized data |
| ER-based and application-oriented | snowflake or start schema-based and subject-oriented |
| Used for transaction processing | Used for data modeling and analysis |
Q3. What are the stages of Data Warehousing?
Answer:
The general stages of the data warehouse are:
- Offline Operational Database: Data is copied from the operating system to another server to perform various operations.
- Offline Data Warehouse: Data in the Data Warehouse is regularly updated from the operational database.
- Real-Time Data Warehouse: The Data Warehouse updates when the operational system experiences any transaction.
- Integrated Data Warehouse: Whenever any transaction occurs within the operational system, it consistently updates the Data Warehouse.
Q4. What is Business Intelligence (BI)?
Answer:
These are the basic Data Warehousing Interview Questions asked in an interview. BI is a technology-driven process for analyzing data and presenting meaningful insights to the end users that helps in better decision-making. BI encompasses various tools that help understand the data trends and patterns hidden in the data. Some widely used tools are SAP Business Intelligence, MicroStrategy, Science, Tableau, and many more.
Q5. What are the components of a Data Warehouse?
Answer:
Four components of the Data Warehouse are:
- Load Manager: It performs all the operations associated with the extraction and load of data into the warehouse.
- Warehouse Manager: It performs operations associated with the data in the warehouse. It performs operations like the analysis of data to ensure consistency, the creation of indexes and views, and many other operations.
- Query Manager: It performs all the operations related to user queries. The operations of this component are direct queries to the appropriate tables.
- End-user access tool: Tools used by end users to access the data. It is categorized into different groups like
- Data Reporting tools
- Query tools
- Application Development tools
- EIS tools
- OLAP and Data mining tools
Part 2 – Data Warehousing Interview Questions (Advanced)
Let us now have a look at the advanced Data Warehousing Interview Questions.
Q6. What is the Dimension table?
Answer:
A dimension table in a data warehouse is a table in a star schema. Dimension tables store dimensions or attributes that describe the data in the Fact table. For example, Product dimension might contain the name, description, unit price, weight, color, and many other attributes. The system uses the key generated to identify a row in the dimension table uniquely. The key acts as a primary key in the dimension table and acts as a foreign key in the fact table, facilitating the joining of the two tables.
Q7. What is a Fact table?
Answer:
A fact table is the center table of the star schema, surrounded by a dimension table of a data warehouse. The fact table consists of the quantitative metrics or facts of the business process. A fact table collaborates with a dimension table and serves as the storage for the data intended for analysis. The fact table contains a foreign key column which acts as a primary key in the dimension table; this key allows joining between these two tables.
Let us move to the next Data Warehousing Interview Questions
Q8. What is Data Mart?
Answer:
Data Mart is a subset of the data warehouse that usually contains specific data related to a particular business line. Data Mart is small and used in querying or analyzing a specific set of data, for example, data related to “Sales,” “Customers,” “Order,” etc.
Q9. What is the Operational Data Store (ODS)?
Answer:
This is the most asked Data Warehousing Interview Questions in an interview. Operational systems use an ODS database to store data before transferring it to a data warehouse. It serves as the intermediate database. An ODS contains short-term data, whereas a data warehouse contains historical data.
Q10. Explain Data Warehouse architecture.
Answer:
It includes the following stages:
- Data Source layer: In this stage, we collect data from various sources and store it in a relational database. Data includes social media data, operational data, transactional data, and many more.
- Data Staging layer: In this stage, the extraction and processing of data from the data source layer occur because the data originates from multiple sources and possesses diverse formats. The extracted data will be subjected to quality checks, and the end results will be clean and organized data that will be loaded into the data warehouse.
- Data Storage layer: This layer will store the data from the staging area as a central repository. Depending upon the business requirements, storage could be a data warehouse, data mart, or an Operational Data Store.
- Data Presentation layer: Users utilize this layer to access the data. Users can perform various queries or run some analysis to perform reports.
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