Wednesday, 11 February 2015

Data Warehousing Concepts Interview Questions and Answers (Page 2)

11. What are data modeling and data mining? Where it will be used?
Data modeling is the process of designing a data base model. In this data model data will be stored in two types of table fact table and dimension table Fact table contains the transaction data and dimension table contains the master data. Data mining is process of finding the hidden trends is called the data mining.

12. What is "method/1"?
Method 1 is system develop lifecycle create by Arthur Anderson a while back.

13. After the generation of a report to whom we have to deploy or what we do after the completion of a report?
The generated report will be sent to the concerned business users through web or LAN.

14. After the complete generation of a report who will test the report and who will analyze it?
After the completion of reporting, reports will be sent to business analysts. They will analyze the data from different points of view so that they can make a proper business decisions.

15. Can you pass sql queries in filter transformation?
We cannot use sql queries in filter transformation. It will not allow you to override default sql query like other transformations (Source Qualifier, lookup)

16. Where the Data cube technology is used?
A multi-dimensional structure called the data cube. A data abstraction allows one to view aggregated data from a number of perspectives. Conceptually, the cube consists of a core or base cuboids, surrounded by a collection of sub-cubes/cuboids that represent the aggregation of the base cuboids along one or more dimensions. We refer to the dimension to be aggregated as the measure attribute, while the remaining dimensions are known as the feature attributes.

17. How can you implement many relations in star schema model?
Many-many relations can be implemented by using snowflake schema .With a max of n dimensions.

18. What is critical column?
Let us take one ex: Suppose 'XYZ' is customer in Bangalore, he was residing in the city from the last 5 years, in the period of 5 years he has made purchases worth of 3 lacs. Now, he moved to 'HYD'. When you update the 'XYZ' city to 'HYD' in your Warehouse, all the purchases by him will show in city 'HYD' only. This makes warehouse inconsistent. Here CITY is the Critical Column. Solution is use Surrogate Key.

19. What is the main difference between star and snowflake star schema? Which one is better and why?
If u have one to may relation ship in the data then only we choose snowflake schema, as per the performance-wise every-one go for the Star schema. Moreover, if the ETL is concerned with reporting means choose for snowflake because this schema provides more browsing capability than the former schema.

20. What is the difference between dependent data warehouse and independent data warehouse?
Dependent departments are those, which depend on a data ware to for their data.Independent department are those, which get their data directly from the operational data sources in the organization.
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