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Data Warehousing Basics Interview Questions and Answers (1)

What are Data Marts ?

A data mart is a focused subset of a data warehouse that deals with a single area(like different department) of data and is organized for quick analysis

What are the steps to build the datawarehouse ?

Gathering bussiness requiremnts
Identifying Sources
Identifying Facts
Defining Dimensions
Define Attribues
Redefine Dimensions & Attributes
Organise Attribute Hierarchy & Define Relationship
Assign Unique Identifiers
Additional convetions:Cardinality/Adding ratios

What is Difference between E-R Modeling and Dimentional Modeling.?

Basic diff is E-R modeling will have logical and physical model. Dimensional model will have only physical model.

E-R modeling is used for normalizing the OLTP database design.

Dimensional modeling is used for de-normalizing the ROLAP/MOLAP design.

Why fact table is in normal form?

Basically the fact table consists of the Index keys of the dimension/ook up tables and the measures.

so when ever we have the keys in a table .that itself implies that the table is in the normal form.

What are the advantages data mining over traditional approaches?

Data Mining is used for the estimation of future. For example, if we take a company/business organization, by using the concept of Data Mining, we can predict the future of business interms of Revenue (or) Employees (or) Cutomers (or) Orders etc.

Traditional approches use simple algorithms for estimating the future. But, it does not give accurate results when compared to Data Mining.

What are the vaious ETL tools in the Market?

Various ETL tools used in market are:
Informatica
Data Stage
Oracle Warehouse Bulider
Ab Initio
Data Junction

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