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Data Warehousing Interview Questions

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Surrogate key

Asked By: mitul arora | Asked On: Jul 27th, 2008

Why do we use surrogate key?

Answered by: Rajesh Swarnkar on: Feb 28th, 2012

Usually Surrogate keys are System Generated keys that can be used in place of missing primary key.

Answered by: sadique_ghitm on: Nov 25th, 2011

A surrogate key in a database is a unique identifier for either an entity in the modeled world or an object in the database. The surrogate key is not derived from application data. A surrogate repres...

What are the possible data marts in life insurance data warehouse project ?

Asked By: janardhanginfa | Asked On: Jul 31st, 2011

Answered by: Rajesh Swarnkar on: Feb 28th, 2012

Data Marts are considered as smaller logical subset of Data warehouse. DW is enterprise-wide while DMs are for Department Level. So DMs can be identified on the basis of what departments are there in Insurance company.
E.g. Sales Department.

Please provide me with interview questions for data quality analyst ?

Asked By: sebastian | Asked On: Jul 25th, 2006

Answered by: surender.Vanga on: Sep 18th, 2011

Here are some questions... (I am assuming that you are asking about Informatica data quality) 1. What are the most used transformations in IDQ? 2. What is address doctor? 3. Can we export an object fr...

Answered by: ravi_kumar_garre on: Nov 11th, 2007

Interview questions for Data Quality Analyst are as follows:
1. How can you say there are no duplicate records in Data warehouse?
2. Whether the ETL job accepts known accept records?
3. What are the Data Quality Tools? e.g. BO Data Quality, First Logic..etc

Kimball and inmon

Asked By: mitul arora | Asked On: Jul 27th, 2008

How anyone define the pracical difference between kimball & inmon?

Star Read Best Answer

Editorial / Best Answer

Answered by: shashk

View all questions by shashk   View all answers by shashk

Member Since Jul-2010 | Answered On : Aug 25th, 2010

Bill Inmon's paradigm: Data warehouse is one part of the overall business intelligence system. An enterprise has one data warehouse, and data marts source their information from the data warehouse. In the data warehouse, information is stored in 3rd normal form.

Ralph Kimball's paradigm: Data warehouse is the conglomerate of all data marts within the enterprise. Information is always stored in the dimensional model.

There is no right or wrong between these two ideas, as they represent different data warehousing philosophies.
In reality, the data warehouse in most enterprises are closer to Ralph Kimball's idea. This is because most data warehouses started out as a departmental effort, and hence they originated as a data mart. Only when more data marts are built later do they evolve into a data warehouse.

Answered by: shashk on: Aug 25th, 2010

Bill Inmon's paradigm: Data warehouse is one part of the overall business intelligence system. An enterprise has one data warehouse, and data marts source their information from the data warehouse...

Degenarated dimension

Asked By: greek143 | Asked On: Aug 11th, 2010

What is the use of degenerated dimension? Where it is used?

Answered by: gargupendar on: Mar 24th, 2011

A degenerate dimension is a dimension which is derived from the fact table and doesn't have its own dimension table.

Example : Receipt number is the perfect example for degenerate dimension.

What is dimension modeling?

Asked By: ravindra kumar | Asked On: Jul 30th, 2006

Answered by: joanitah on: Mar 12th, 2011

This is a process and outcomes of modeling a logical database schemas created to support OLAP and data warehousing solutions.

Answered by: Hakoonamatata on: Jul 9th, 2007

Here's a different way to look at dimensional modelling:Consider data to be a flat table for now. It would have some columns that contain numbers that need to be used in calcualtions later (e.g. b...

Tracing options available in data warehousing

Asked By: Muthu3180 | Asked On: Jan 20th, 2008

What are the different tracing options available? Can tracing options be set for individual transformations?

Answered by: joshmohit on: Nov 3rd, 2010

I am not sure if this pertains to the datawarehouse in general but we do have concept of audit dimensions. Also, dimensions with effective dating can help tracing the changes.

Answered by: sraghav20 on: Oct 7th, 2010

I guess, this question should be directed towards particular tools... as a concept, data warehousing would be hard pressed to have any logging...

Importance of SCD

Asked By: gpadma.ds | Asked On: Sep 19th, 2010

How is SCD helpful in real time? Give example by taking banking project.

Answered by: rummyraj on: Oct 13th, 2010

Customer dimension is a good example. Customer address and Phone number frequently changes. So you will update the customer dimension for these changes.Hence its called as SCD. There are several types though. This example is type1 SCD.

A dimension table is wide but the fact table is deep explain the statement in your own words.

Asked By: Saba | Asked On: Nov 5th, 2007

Answered by: sraghav20 on: Oct 7th, 2010

Visualize it...You need more lookup data to fit in a single row in dimensions.. Its lookup data, it wont have as many records as the fact, but it would have far more columns. A Visually, if you think...

Answered by: ramonasiraj on: Jul 21st, 2008

A dimension table contains details about subject area. Eg. customer , product

Fact table contains all business measures ( numeric value) and foreign key value.

What is the data type of the surrogate key?

Asked By: pepsi | Asked On: Jul 18th, 2007

Answered by: sneha bhatt on: Sep 29th, 2010

Always integer or numeric

Answered by: tirukosri on: Jun 4th, 2008

Surrogate keys are the system generated keys and used to eliminate the redundancy in the primary keys. So they are always integer numbers.

What is the main difference between star and snowflake star schema? Which one is better and why?

Asked By: Interview Candidate | Asked On: Jan 19th, 2007

Answered by: bcsandip on: May 25th, 2010

Star Schema: 1. Dimension tables directly connected to Fact Table2. Contain de-normalized data3. Data modifications are very easily4. Highest flexibility5. Best performance6. Takes more memory space t...

Answered by: geetu rani on: Mar 27th, 2008

STAR SCHEMA HAS fact table linked with dimension table directlywhile in snow flake schema the dimension tables can have futher hierarchies between them .it means in snow flake schema the tables are no...

What is the difference between database and data warehousing?What is the main advantages of data warehousingwhat is mean by data stagewhat is the famous tools used for data warehousing?What is the architecture...

Asked By: s.Narasimma subramanian | Asked On: Feb 1st, 2006

Answered by: brahmiii on: Feb 28th, 2010

Database is the root of any data releted operations where as datawarehousing is a schema or process how effectively we access or utilize a database. Datawarehousing follows the star schema and snowflake schema as its basic schemas and we two other schemas also which are not much important.

Answered by: sap_23 on: Sep 3rd, 2009

Database: A database is used to record, retrieve, update business transactions which are occurred daily in business life. Data ware House: A data warehouse is used to record historical data, purely for analysis purpose for top management.

Staging and operational data store

Asked By: WISDOMBOWL | Asked On: Feb 22nd, 2009

What are staging and operational data stores and what is their difference? why does one need staging and why does one need ods? What will happen if they are not there? Who and how is it decided that a staging or ods is needed? Which comes first staging or ods?

Answered by: jryan999 on: Feb 3rd, 2010

An Operational Data Store (ODS) is a repository of active "operational" data.  It's typically used to hold data for a short period (eg. Days or weeks at most), to help the business ...

Answered by: srilu1234 on: Jan 19th, 2010

Stagining and operational data store are different databases.It can be one database aswell to reduce the cost to maitain two databases.Staging is the place where cleansing is done and Operational Stor...

What is data cleaning? How can we do that?

Asked By: GeekAdmin | Asked On: Oct 4th, 2006

Answered by: sub_guha on: Jan 24th, 2010

Data cleaning, technically called "Data Cleansing"is a group of methods for making data more reliable and accurate. Usually companies store data in warehouses so they can make meaning out of...

Answered by: Hakoonamatata on: Jul 9th, 2007

Data cleaning is a self explainatory term. Most of the data warehouses in the world source data from multiple systems - systems that were created long before data warehousing was well understood, and ...

Ooad object oriented analysis & design

Asked By: mitul arora | Asked On: Jul 27th, 2008

When is the need to do ooad (object oriented analysis & design)

Answered by: subang on: Jan 16th, 2010

We use OOAD in order to design the system when overall requirements needed for developing the new system are clearly understood by the developer.

Data mart data

Asked By: shopperstop47 | Asked On: Oct 10th, 2009

Is data, transient or periodic in data mart? Explain

Answered by: ashishsinha.dummy on: Nov 10th, 2009

Data marts are part of OLAP system. Data in datamarts cannot be trasient. Data will be updated in datamarts on a periodic or daily basis depending on the design of the data warehouse.
-Ashish

If you source data from a system that you (warehouse team) have no authority to enforce data quality at the source level, how do you handle this? Do you apply data validation just after you stage the data?...

Asked By: sreya | Asked On: Oct 31st, 2006

Answered by: Dominique on: Sep 9th, 2009

A DW is no longer relevant when it contains inconsistent data. The strength of a DW - and its robustness - also relies on the validation processes... The sooner you can detect and report any inconsist...

Answered by: Nitin on: Mar 17th, 2007

One of the main purpose of Datawarehousing is to get Cleanse data.
So skipping data validatons is not a good idea.
It will be better to bring the data to a staging area and perform validations.
Or while pushing data from the source we can perform data validations.

Lookup performance

Asked By: mukta_kelkar | Asked On: Mar 18th, 2009

How does the usage of dataset improve the performance during lookups?

Answered by: sixto.dsilva on: Aug 17th, 2009

Correct me if i misunderstood your question. I think you want to know whether the usage data will improve the graph performance. I think definitely the usage of data will definitely improve the graph ...

Data warehouse as transaction database

Asked By: jamx100 | Asked On: Mar 19th, 2009

Can a data warehouse also be used for transaction database? If yes why, if no why not?

Answered by: sixto.dsilva on: Aug 15th, 2009

As the definaton of Datawarehouse say it is repository of historial data which is used by Busines users to run some reports on his/her area of interests.Data is not loaded everyhour or every mtes in D...

Answered by: SQLGal on: Jun 7th, 2009

No, a data warehouse cannot by definition be used as a transaction database.  A data warehouse is "read only" data that does not change once it has been loaded and used for informa...

What is the difference between mapping parameter & mapping variable in data warehousing?What are the types of variable available in data warehousing?

Asked By: vikram | Asked On: Jul 23rd, 2007

Answered by: dhiveya.m on: Apr 22nd, 2009

Mapping parameter are the constant values (values never changes) and mapping variables are the values that ever changes.

Answered by: fir_dan on: Jul 18th, 2008

A mapping parameter is a static value that you define before running the session and it retains the same value till the end of the session. Define a parameter in paramaeter file (.par) and use it in m...

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