DWH Interview Questions

What is an ODS?

 http://prashanthobiee.blogspot.in/2012/12/operational-data-store.html

What is a Federated Data Warehouse?

 http://prashanthobiee.blogspot.in/2012/12/federated-data-warehouse.html

What is a Virtual Data Warehouse?

 http://prashanthobiee.blogspot.in/2012/12/virtual-data-warehouse.html

What is an Enterprise Data Warehouse?

  http://prashanthobiee.blogspot.in/2012/12/enterprise-data-warehouse.html

What are the different process maps available for Data Marts?

http://prashanthobiee.blogspot.in/2012/12/different-process-maps-for-data-marts.html

What is Top-Down architecture of Warehouse development?

 http://prashanthobiee.blogspot.in/2012/12/top-down-architecture-of-warehouse.html

What is Bottom-up architecture of Warehouse development?

http://prashanthobiee.blogspot.in/2012/12/bottom-up-architecture-of-warehouse.html 

What is Enterprise Data Mart architecture of Warehouse development?

http://prashanthobiee.blogspot.in/2012/12/enterprise-data-mart-architecture-of.html 

What is Data Stage/ Data Mart architecture of Warehouse development?

http://prashanthobiee.blogspot.in/2012/12/data-stage-data-mart-architecture-of.html  

What is Distributed Data Warehouse/ Data Mart architecture of Warehouse development?

 http://prashanthobiee.blogspot.in/2012/12/distributed-data-warehouse-data-mart.html 

What is Normalization, First Normal Form, Second Normal Form , Third Normal Form?

 1.Normalization is process for assigning attributes to entities–Reduces data redundancies–Helps eliminate data anomalies–Produces controlled redundancies to link tables

 2.Normalization is the analysis of functional dependency between attributes / data items of user views,It reduces a complex user view to a set of small and stable subgroups of fields / relations

1NF: Repeating groups must be eliminated, Dependencies can be identified, All key attributes defined,No repeating groups in table

2NF: The Table is already in1NF, includes no partial dependencies–No attribute dependent on a portion of primary key, Still possible to exhibit transitive dependency, Attributes may be functionally dependent on non-key attributes.

3NF: The Table is already in 2NF, Contains no transitive dependencies

Why do we need a different schema for Data warehousing/Business Intelligence?

 A data warehouse stores historical data that is collected from various sources and the data is time variant. The data warehouse is updated in a scheduled and controlled manner. An online system usually does not store historical data, however if history data is stored it would pose severe performance issues, further being an Online environment 2 users accessing the same set of information are likely to derive different results. An online system would provide data only from a single source, whereas a data warehouse usually has data being put in from various sources.

What are the various features of Enterprise Data Warehouse?

 The various features of an EDW are:

 An EDW may or may not interact with Data Mart. The most important aspect of any Data Warehouse is the consistency of information.

An EDW may have same level of granularity as a Data Mart. This means that the data from the Data Mart will be dumped into an EDW.

An EDW may have more detailed level of data than a Data Mart. This means that the data requirement is at a more granular level that may not be catered by the Data Mart.