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DATAWAREHOUSING INTRODUCTION



DATA WAREHOUSING    

Data warehousing is a relational database which is used to store large volumes of data for analyzing business but not for business transaction processing

•       A DWH is designed to support decision making process. Hence it is known as Decision Support System(DSS)

•       It analyzes the business transactions in order to support decision making

•       DWH is a container data

•       DWH is the process of developing a data warehouse

•       DWH is a read only database because it is designed to read the data for analysis but not for transactional processing

•       DWH is a historical database because it can store historical business information

•       Father of Data warehousing  W.H.Inmon.In 1987, he designed a data warehouse

 Problems in existing systems:

•       Data is scattered around multiple operational systems

•       Inconsistency of the data across multiple transactional systems

•       Volatile data

•       Increasing complexity of reporting needs

 Business Analyst: Collects the requirements of a business

Data Architect: Designs DWH

ETL Developers

Report Authors

 GUI ETL Tools Ex: Informatica,Datastage

Reporting Tools Ex: Cognos, BI XI

 Data warehouse is a:

subjectoriented,integrated,non-volatile,time

variant database in support of management

decision-W.H.Inmon

 Subject oriented:

Tables in DWH has to be concentrated on subject

Ex: Products,Customers,Sales

Integrated:

     When we bring data from multiple sources, we need to make sure that the data has to be in

uniform format

 Ex:     

USA                  

 CustName Gender

  XXXX            M
  XXXX            F

INDIA

CustName   Gender

 XXXX       Male
 XXXX       Female

GERMANY

CustName   Gender

XXXX       0

XXXX       1


 Non volatile:

In DWH data is for read only

Time variant:

To compare business across time

 Time

Year

Quarter

Month

Week

Day

Datamart:

It is a subset of DWH, address single

business process

Ex: Sales, Marketing, Finance

•       It is a high performance query structure(HPQS)

•       Fast retrieval of data

 

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