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Data warehouse Latest Interview Questions and Answers Part-2

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datawarehouse11. What is the difference between View and Materialized View?
A view is nothing but a virtual table which takes the output of the query and it can be used in place of tables.

A materialized view is nothing but an indirect access to the table data by storing the results of a query in a separate schema.

12. What is ETL?

ETL is abbreviated as Extract, Transform and Load. ETL is a software which is used to reads the data from the specified data source and extracts a desired subset of data. Next, it transform the data using rules and lookup tables and convert it to a desired state.

Then, load function is used to load the resulting data to the target database.

13. What is VLDB?

VLDB is abbreviated as Very Large Database and its size is set to be more than one terabyte database. These are decision support systems which is used to server large number of users.

14. What is real-time datawarehousing?

Real-time datawarehousing captures the business data whenever it occurs. When there is business activity gets completed, that data will be available in the flow and become available for use instantly.

15. What are Aggregate tables?

Aggregate tables are the tables which contain the existing warehouse data which has been grouped to certain level of dimensions. It is easy to retrieve data from the aggregated tables than the original table which has more number of records.

This table reduces the load in the database server and increases the performance of the query.

16. What is factless fact tables?

A factless fact tables are the fact table which doesn’t contain numeric fact column in the fact table.

17. How can we load the time dimension?

Time dimensions are usually loaded through all possible dates in a year and it can be done through a program. Here, 100 years can be represented with one row per day.

18. What are Non-additive facts?

Non-Addictive facts are said to be facts that cannot be summed up for any of the dimensions present in the fact table. If there are changes in the dimensions, same facts can be useful.

19. What is conformed fact?

Conformed fact is a table which can be used across multiple data marts in combined with the multiple fact tables.

20. What is Datamart?

A Datamart is a specialized version of Datawarehousing and it contains a snapshot of operational data that helps the business people to decide with the analysis of past trends and experiences. A data mart helps to emphasizes on easy access to relevant information.

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