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Data Warehousing Basics

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Hld, lld , mapping documents

Asked By: gajaa | Asked On: Oct 15th, 2014

What is high level document(hld),lowlevel document(lld),mapping documents ? What is the stuff they contains?

What is lld and hld ?

Asked By: gajaa | Asked On: Oct 15th, 2014

What is low level document(lld) and high level document(hld) and mapping document what they contain?

What is data cleaning? How is it done?

Asked By: sahira2000 | Asked On: Oct 2nd, 2006

Answered by: abhishek on: Sep 28th, 2014

It is a first step of data warehousing . there we are validating and verifying data come from number of source than load in ODS it called delta loading or staging area or cleaning stage.

Answered by: Gvkishore on: Jan 16th, 2012

Could you please give me one real time example How we do data cleansing.....

What are the various reporting tools in the market

Asked By: Interview Candidate | Asked On: Jun 8th, 2005

Answered by hemakumar on 2005-04-12 05:40:50: cognos businessobjects microstrategies actuate

Answered by: Bharath on: Aug 27th, 2014

Pentaho Data Analytics

Answered by: Ravi on: Aug 21st, 2014

IntelliView INEA
Business Objects (Crystal Reports)
Cognos (Impromptu, Power Play)
MS reporting services(SSRS)
Informatica Power Analyzer
Hyperion (BRIO)
Oracle Express OLAP
jasper reports

What are the different methods of loading dimension tables

Asked By: Interview Candidate | Asked On: Jun 28th, 2005

Answered by: mukul konch on: Aug 16th, 2014

The data in the dimension tables may change over a period of time. Depending upon how you want to treat the historical data in dimension tables, there are three different ways of loading the (slowly)...

Answered by: kevin0209 on: Aug 30th, 2010

Conventional Load: Before loading the data, all the Table constraints will be checked against the data. Direct load: (Faster Loading) All the Constraints will be disabled. Data will be loaded directly. Later the data will be checked against the table constraints and the bad data won't be indexed.

Which automation tool is used in data warehouse testing?

Asked By: Chaitra Bharadwaj | Asked On: Jan 9th, 2006

Answered by: ora.amar on: Aug 5th, 2014

We can use Data Validation option DVO provided by informatica corporation to automate etl testing.

Answered by: bhayduk on: Sep 21st, 2011

We have tried QTP from HP and RFT from IBM. Both can launch SQL and you can script around doing the result compares but it is not easy. we now use QuerySurge.

What is the difference between data warehousing and business intelligence?

Asked By: quontra123 | Asked On: May 24th, 2014

Try to answer if you know

Answered by: Anil on: Jul 25th, 2014

DWH helps you store the data while BI controls data for decision making, forcasting

Answered by: Shrikanth on: Jun 12th, 2014

Data warehousing is a method to store the data in specially designed database. where as business intelligence processes the data in data warehouse to make some business decision.

What is a data warehousing?

Asked By: Interview Candidate | Asked On: Aug 25th, 2005

Data warehouse is a repository of integrated information, available for queries and analysis. Data and information are extracted from heterogeneous sources as they are generated....This makes it much easier and more efficient to run queries over data that originally came from different sources. Typical...

Answered by: Avik Saha on: Jul 2nd, 2014

Data Warehouse is an electronic storage of an organization of historical data for the purpose of analysis,reporting,data mining or knowledge discovery.

Data warehouse is a collection of set of information as well as supporting system.

Answered by: mukku on: Feb 25th, 2014

A data warehouse is a powerful database model that enhances the users ability to quickly analyze large and multinational data sets.. data warehouse changes and organizes data to allow users to make b...

What is surrogate key ? Where we use it explain with examples?

Asked By: Minish Cherian | Asked On: Oct 18th, 2005

Star Read Best Answer

Editorial / Best Answer

Answered by: saravanan

Answered On : Dec 2nd, 2005

Surrogate key is a unique identification key, it is like an artificial or alternative key to production key, bz the production key may be alphanumeric or composite key but the surrogate key is always single numeric key. Assume the production key is an alphanumeric field if you create an index for this fields it will occupy more space, so it is not advisable to join/index, bz generally all the datawarehousing fact table are having historical data. These factable are linked with so many dimension table. if it's a numerical fields the performance is high

Answered by: Abdulhakim on: Jun 26th, 2014

Surrogate keys are keys used in identifying other keys like

Answered by: rj_dwbi on: Apr 2nd, 2012

Surrogate key is a numeric or integer value in a table to identify each row uniquely. Primary key and surrogate key are same but surrogate key is a system generated value has a define incremental valu...

What is the difference between Informatica and obiee?

Asked By: Nash Nareshkumar | Asked On: Feb 12th, 2014

Answered by: Ankit Kansal on: Feb 15th, 2014

INFORMATICA is a data integration and warehousing tool which prepares data from different sources to a stream line flow after which a tool like OBIEE uses that data to display reports in several formats e.g. Charts & Graphs

How to define cardinality between dimension and fact ?

Asked By: harsha.varigonda | Asked On: Jan 13th, 2014

Answered by: Piyush Shah on: Feb 5th, 2014

One to many.

What is SCD1 , SCD2 , SCD3

Asked By: Interview Candidate | Asked On: Jul 28th, 2005

Answered by: kalyan on: Nov 22nd, 2013

The value of dimensions is used change very rarely, That is called Slowly Changing dimensions.

they are 3 types


scd1:it used Replace the old values overwrite by new values
scd2:Creating Additional records
scd3:Its maintain just previous and recent

Answered by: sharuvijay on: Jan 28th, 2009

SCD1-> Slowly Changing Dimension Type1This type will overwrite new records with old records without caring about the history.SCD2-> Slowly Changing Dimension Type2This type will create a duplica...

How can I verify the latest data from above table?

Asked By: govkj | Asked On: Oct 27th, 2013

I have a table with two columns name namely current,history but I dont have time stamp to make sure that when the data is updated or deleted. now how can I verify the latest data from above table?

Answered by: fazal on: Oct 29th, 2013

Select max (ora_scan) from table;

Select scn_to_timestamp (the_above_output) from dual;

What is the difference between star schema and snow flake schema? When we use those schema's?

Asked By: swarna | Asked On: Nov 23rd, 2006

Answered by: sunny on: Jul 5th, 2013

star schema: When dimension table contains less number of rows, we can go for Star schema.In this Both Dimension and Fact Tables are in De-Normalized form.Good for datamarts with simple relationships ...

Answered by: shakilag on: Jun 23rd, 2009

Star Schema: A single fact table associated to N dimension tables. This schema is denormalised and hence has good performance as this involves a simple join rather than a complex query.Snowflake schem...

What is the difference between oltp and olap

Asked By: Interview Candidate | Asked On: Jun 5th, 2005

Answered by swetha on 2005-03-30 12:00:33: oltp  current data short database transactions online update/insert/delete normalization is promoted high volume transactions transaction recovery is necessary   olap current and historical data long...

Answered by: ShivaRam on: Jun 22nd, 2013

Hey add these points also, 1)OLTP:Volatile data behavior OLAP:Non-volatile data behavior 2)OLTP:More no of Users OLAP:Less no of Users 3)OLTP:E-R model for data modeling OLAP:Dimension model for data...

Answered by: keerthi on: Feb 1st, 2012

OLTP: 1.insert/update 2.thousands of users 3.size 1gb to 4gb to day operations 5.transaction of data,detailed data 6.application oriented OLAP: 2.hundreads of people(only d organiz...

Why fact table is in normal form?

Asked By: mallikharjuna reddy | Asked On: Mar 13th, 2006

Answered by: j123 on: Jun 9th, 2013

Foreign keys of facts tables are primary keys of Dimension tables. It is clear that fact table contains columns which are primary key to other table that itself make normal form table.

Answered by: Sanjeev on: Mar 26th, 2007

The Fact table is central table in Star schema, Fact table is kept Normalized because its very bigger and so we should avoid redundant data in it. Thats why we make different dimensions there by makin...

Give examples of degenerated dimensions

Asked By: stalin | Asked On: Jul 17th, 2006

Answered by: mahesh on: Feb 2nd, 2013

A source table has a single column, we not transfer this column to dimension table, directly to connected to the fact table ,this fact table called the de-generated dimensional table

Answered by: mri_sonam on: Dec 18th, 2008

Best example is "Invoice Number","bill number","PO Number", these all are degenerated dimensions in the Transaction Tables, they can be maintained in the fact table itself instead of  crating seperate dimensions for this.

Do u need seperate space for datawarehouse & data mart

Asked By: chramgopal | Asked On: Oct 24th, 2006

Answered by: moluguri on: Aug 30th, 2012

I think, we don't need separate space for Data Warehouse and Data Mart. Data Warehouse is a collection of Data Marts. Data Mart is a particular line of business..

Answered by: Gvkishore on: Jan 16th, 2012

Why so.....Is there any advantage creating the DWH after creating the Datamarts...?

what is the use of Vice versa...?

What is rapidly changing dimension?

Asked By: Deeprekha | Asked On: Jul 27th, 2006

Answered by: dipanshu handoo on: May 26th, 2012

A dimension is considered to be a rapidly changing dimension if one or more of its attributes changes frequently in many rows. For a rapidly changing dimension, the dimension table can grow very large from the application of numerous Type 2 changes.

Answered by: juha_teuvonnen on: Jul 11th, 2007

A rapidly changing dimension is a result of poor decisions during the requirements analysis and  data modeling stages of the Data Warehousing project. If the data in the dimension table is changing a lot, it is a hint that the design should be revisited.

What are the vaious etl tools in the market

Asked By: Interview Candidate | Asked On: Aug 31st, 2005

Answered by: Ashutosh Shukla on: May 4th, 2012

1. Oracle Warehouse Builder (OWB) 11gR1 Oracle 2. Data Services XI 3.2 SAP Business Objects 3. IBM Information Server (Datastage) 9.1 IBM 4. SAS Data Integration Studio 4.21 SAS Institute 5. Pow...

Answered by: saurabh on: Aug 1st, 2011

ODI is the future of all ETL tools..because its E-LT not ETL.

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