Data Warehouse Interview Questions


Well begun is half done. Those who agree to this saying will definitely recognize the importance of preparing well for an interview. It is after working hard and applying to numerous agencies that one gets an opportunity of an interview. It makes no sense of working so hard if you end up ruining this chance and failing at the interview. Hence, it is vital to make all preparations and gather sufficient knowledge that will help you acquire your dream job. One can prepare themselves by sharpening their knowledge and finding answers to frequently asked interview questions. Hence, we have prepared a list of data warehouse interview questions to aid the job searching needs of the candidates.

We have tried answering these questions impressively such that it helps the candidates to convince the recruiter of his knowledge and capabilities. We are hopeful that these sample questions will help you to gain the necessary confidence.

  1. How do you define data warehouse?

    Answer: Data warehouse is a database that is used to store information for the purpose of analysis. The data pertains to a specific subject alone. It is time variant and non volatile, which means that the information once loaded will not get deleted and the data is subject to change with respect to time.

  2. How do you think is data warehouse useful?

    Answer: Data warehouse allows the user to store abundant information in one place. It helps to integrate voluminous information and analyze it from any perspective. It has made data analysis and data integration easy and simple. The gathered information can be utilized to make formulas and forecast the trends for the future.

  3. Point out the differences between data warehousing and data mining.

    Answer: Data warehousing refers to the task of storing information in the database. Data is gathered from different sources and cleaned to sort out relevant information. The sorted data is added to the warehouse. On the other hand, data mining is exploring the warehouse. Data is mined out by entering queries into the system.

  4. Explains the ETL process in Data warehouse.

    Answer: ETL is an acronym for extract, transform and load, which basically are the three steps in this process. Extract includes extracting information of an expected pattern or structure from multiple databases. This stage sets the base for next two steps. Transform includes a set of rules and instructions that is required to process the information before using it for the end target. Load refers to the final stage where information is actually loaded into the data warehouse.

  5. What is meant by OLAP and OLTP? State the similarities or differences between them.

    Answer: OLAP stands for OnLine Analytical Processing whereas OLTP stands for OnLine Transaction Processing. OLAP concerns archival data that is important for statistical analysis, while OLTP concerns operational data, which is important as commands for operating a system. Operational data is subject to updating. It is easier to find data regarding an individual unit by way of queries. Analytical data is less prone to updates and requires voluminous data and number of aggregations. Thus, we can conclude that OLAP is a processing system that facilitates analysis of data by utilizing information from all spheres and performing complex calculation, while OLTP is an application that manages voluminous transactions by way of commands.

  6. Define data marts?

    Answer: Data marts are small sections of information gathered from voluminous corporate data that caters to the requirements of a specific group. Independent data mart includes the data gathered from sources of OLTP systems, external providers and local department. Dependent data mart is information gathered from the official data warehouse of the enterprise.

  7. Describe the steps in building the data warehouse

    Answer: First step is to gather business information and understand the requirements. Second step is to identify the sources that would provide relevant and accurate information. Third , verify the gathered information and check for accuracy. Fourth, define the dimensions and attributes that would give a definite structure to it. Fifth, organize the hierarchy levels for attributes and define relation between each element. Sixth, apply uniques identifiers to the system and lastly, add conventions and ratios to the system.

  8. What is Meta Data

    Answer: Meta data means data of data. It gives information to the user about the data's elements such as number of columns, data type, fields, ordering of fields, etc.

  9. Can you name a few popular reporting tools used in the market?

    Answer: There are many reporting tools that are commonly used in market. They are cognos, microstrategy, actuate, hyperion, proclarity, etc.

There are several question on data structure. We have given here a few questions. You can write your own answers for the same.

  1. Define surrogate key and dimensional key
  2. What is meant by hybrid design model?
  3. Define and differentiate between fact tables and dimensional tables.
  4. Can you explain any disadvantages of data warehousing
  5. What is SCD?
  6. What is normalization? Explain First Normal Form, Second Normal Form and Third Normal Form.
  7. Tell me more about recovering sessions
  8. How is data modeling important?
  9. What is meant by aggregate tables?

Resume writing is an apparent task in job search. However, interview is at the crux of it. While resume gives an entry to the candidate in the organization, it is the interview that seals his position in the organization. Analysis made at the interview determines if the person deserves to work at that position or not. It separates the winner from the crowd. Interview gives one chance to prove one's mettle and it should not be wasted away. Hence, we request the job seekers to give their best shot at the interviews and gain the confidence of the recruiters. We hope this list of data warehouse interview questions prove beneficial in this task.


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