What is hybrid slowly changing dimension?
Let me give an example to make the point clear…. Like account information is usually maintained in two categories: Current Account and other is Time of Event... Read more »
Archive for September, 2008
Can a dimension table contains numeric values?
A dimension table can contain anything you want - it is the business requirements around each data element that drive the data model. Eg: Your company makes bicycles.... Read more »
Explain degenerated dimension in detail ?
A Degenerate dimension is a Dimension which has only a single attribute. This dimension is typically represented as a single field in a fact table. The data items... Read more »
What is the need of surrogate key;why primary key not used as surrogate key Surrogate key is system generated unique number ?
Identity in SQL, Sequence in Oracle, Sequence Generator in Informatica. For Example : You are extracting Customer Information from OLTP Source and after ETL process,... Read more »
What is data cleaning? how is it done?
It is nothing but purifying data , the extract process always exposes the data qulaity issues that have been bured within the operational source system. Since the... Read more »
How data in datawarehouse stored after data has been extracted and transformed from hetrogeneous sources and where does the data go from datawarehouse ?
Data will stored in fact’s and dimensional tables, the relational database can be Oracle, Informatic or netezza, it purely depends upon the company which technology... Read more »
Do u need seperate space for Datawarehouse & Data mart ?
IN THE DATAWARE HOUSE ALL THE INFORMATION OF THE ENTERPRISE IS THERE BUT THE DATA MART IS SPECIFIC FOR THE PARTICULAR ANALYSIS LIKE SALES,PRODUCTION ….,,,... Read more »
Summarize the differene between OLTP,ODS AND DATA WAREHOUSE ?
oltp - means online transaction processiing ,it is nothing but a database ,we are calling oracle,sqlserver,db2 are olap tools. OLTP databases, as the name implies,... Read more »
Whatis cube and why we are crating a cube what is diff between etl and olap cubes any budy ans plz?
Any schema or Table or Report which gives you meaningful information of one attribute wrt more than one attribute is called a cube. For Ex: In a product table... Read more »
What is the difference between star schema and snow flake schema ?and when we use those schema’s?
Star Schema : Star Schema is a relational database schema for representing multimensional data. It is the simplest form of data warehouse schema that contains one... Read more »
What is difference between BO, Microstrategy and Cognos?
BO is a ROLAP Tool, Cognos is a MLAP Tool and MicroStrategy is a HLAP Tool Read more »
What is the role of surrogate keys in data warehouse and how will u generate them?
A surrogate key is a simple Primary key which maps one to one with a Natural compound Primary key. The reason for using them is to alleviate the need for the query... Read more »
What is source qualifier?
Source qualifier is one of transformations in Informatica that helps you define the basic data set that needs to be loaded to the target system. This is one of the... Read more »
What are the various attributes in time dimension, If this dimension has to consider only date of birth of a citizen of a country?
* Date and time (If datetime data type is not supported then you have to have hour/min/sec on a Seperate columns) * Week * Month * Quarter * Year Read more »
Explain the flow of data starting with OLTP to OLAP including staging ,summary tables,Facts and dimensions ?
OLTP(1)—->ODS(2)——>DWH(3)——–>OLAP(4)————>Reports(5)——>decision(6) 1-2 (extraction) 2-3 (Transformation... Read more »