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Data Modeling Interview Questions

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What is data sparsity and how it effect on aggregation?

Asked By: pathan afzal | Asked On: Dec 29th, 2005

Answered by: SC on: Mar 9th, 2006

Data sparsity is term used for how much data we have for a particular dimension/entity of the model. It affects aggregation depending on how deep the combination of members of the sparse dimension mak...

What is the difference between hashed file stage and sequential file stage in relates to datastage server?

Asked By: srinu | Asked On: Sep 23rd, 2005

Answered by: SRIKANTH on: Sep 4th, 2006

SEQUENTIAL FILE CANT BE USED AS LOOK UP.. || HASHED FILE CAN BE USER AS LOOK UPIN SEQ.FILE REMOVING DUPLICATES IS DIFFICULT ||IT MAINLY WORKS AS HASHING ALGORITHM WITH OUT ANY KEY COLUMN IT WONT COSIDER..HASHED FILE IS UR FOR BETTER PERFORMANCE..WE INCREASE THE SIZE OF THE BUFFER IN TIS..

Answered by: sangroover on: Feb 14th, 2006

Hash file is helpful to take data from any coloumn, it will also have a key, as it has the key the data is sorted.

wHEN

Generally speaking,for a weak entity set to be meaningful it must be part of a 1. One-to-one relationship 2. One-to-many relationship 3. Many-to-many relationship 4. Depends on a particular situation

Asked By: Rujul | Asked On: Mar 9th, 2007

Answered by: Ritu Khare on: May 12th, 2007

A weak entity is a part of one-to-many relationship, with the identifying entity onĀ one-side of the relationship, and with total participation on many-side. The weak entity relies on the identifying ...

What is first normal form ?

Asked By: Interview Candidate | Asked On: Jul 18th, 2005

Answered by: Sujatars on: Jun 15th, 2007

First Normal Form sets the basic structure for an organized database by
1. Eliminating the duplicate/repetative columns from the same table.
2. Create a seperate table for each set of related data and identify each set of related data (row) with a unique column (primary key).

Answered by: vvijaychandra on: Jun 24th, 2006

eliminate the repeating groups in the individual tables

create a seperate table for each set of related data.

identify each set of related data with a primary key

What is second normal form ?

Asked By: Interview Candidate | Asked On: Jul 18th, 2005

Answered by: Sujatars on: Jun 15th, 2007

Second normal form (2NF) addresses the concept of removing duplicative dataMeet all the requirements of the first normal form. Remove subsets of data that apply to multiple rows of a table and pl...

Answered by: vvijaychandra on: Jun 24th, 2006

create seperate tables for the set of values that apply to multiple records , realate these tables with a foreign key.

Why are recursive relationships are bad? How do you resolve them?

Asked By: Interview Candidate | Asked On: Jul 21st, 2005

Answered by: Jeetendra Nalawade on: Nov 12th, 2007

We have used a different way of maintaning recursive relationship. We have created a ancestry table which will give the childs for each entry upto n th level. This way you can fire queries directly to get the child upto any specific level.

Answered by: ritwik roy on: Jul 21st, 2005

using the concept of self join may be a solution to this problem. e.g if a table called employees contains three fields like emp_id,name and manager_id and we will have to find out the name of the ma...

In which normal form is the dimension table and fact table in the schema?

Asked By: madhu2732 | Asked On: Nov 11th, 2007

Answered by: SashaFroyland on: Mar 1st, 2008

Unlike OLTP, the goal of dimensional and fact modeling is not to achieve the highest Normal Form but rather to make key performance indicators (often sought after measures) readily accessible to ad-do...

Answered by: canrizt on: Jan 21st, 2008

Every schema deals with Facts and Dimensions.Fact will be the central table in the Schema were as Dimensions Table are the surrounded table of Fact.Dimensions table is one who give the description of ...

What is the difference between logical data model and physical data model in erwin?

Asked By: arnab | Asked On: Nov 22nd, 2007

Answered by: SashaFroyland on: Mar 1st, 2008

The only difference is in what's been selected in the model type when the diagram was first started. In ERWin 7.3 you have the choice of creating three different kinds of diagrams: 1) Physical...

Answered by: rahul.katke on: Dec 27th, 2007

The Logical Data Model (LDM) is derived from the Conceptual Data Model (CDM).The CDM consists of the major entity sets and the relationship sets, and does not state anything about the attrib...

How we are going to decide which schema we are going to implement in the data warehouse?

Asked By: madhu2732 | Asked On: Nov 11th, 2007

Ie. Whether it should be star schema or snow flake schema?

Answered by: SashaFroyland on: Mar 1st, 2008

Pro Star Schema: Users find easier to query and faster query times. Space consequences of repeated data makes little difference as Dimensional table hold relatively fewer rows then the la...

Describe the third normal form?

Asked By: Interview Candidate | Asked On: Aug 23rd, 2005

Answered by: vas_kal on: May 11th, 2008

3NF allows transitive dependency

Answered by: Sujatars on: Jun 15th, 2007

Remove columns that are not dependent upon the primary key

Data modeling software tools

Asked By: King Xirol | Asked On: Oct 18th, 2007

What are the different data modeling software tools? Which one is considered the best among all in terms of cost, efficiency and usability ?

Answered by: geeksds on: Sep 18th, 2008

Visio; ERwin; Rational.  Rational is considered the best.   

Answered by: SashaFroyland on: Mar 1st, 2008

ERWin is the industry leader.

When should you consider denormalization?

Asked By: Interview Candidate | Asked On: Aug 23rd, 2005

Answered by: geeksds on: Sep 18th, 2008

When there are performance issues, that would be improved by denormalizing the database.

Answered by: sachin on: Jun 25th, 2007

There are various reasons behind normalizing and denormalizing.If you dig deep into the practical world, everywhere all the applications have both type of formation. You cannot deal with only one type...

Relational and dimensional data modeling

Asked By: tushardriems | Asked On: Oct 30th, 2008

How does relational data modeling differ from that of dimensional data modeling?

Answered by: wmilford on: Jan 15th, 2009

In relational models data is normalized to 1st, 2nd or 3rd Normal form. In dimensional models data is denormalized. The typical design is that of a Star where their is a central fact table containing...

Spiral model and risk analysis

Asked By: josande31 | Asked On: Feb 1st, 2009

Specify and explain examples of the types of projects that benefit and the types of projects that suffer from the regular placement of risk analysis within the spiral model.

Components of information system architecture

Asked By: maxmadhav | Asked On: Aug 6th, 2008

List six key components of information system architecture. Which of these relate to database design and why?

Answered by: MAbdullah47 on: Feb 9th, 2009

1. Data 2. Processes 3. Network 4. People 5. Events and points in time 6. Reasons All of them related to the DB Design . During the database design we need data to define it’s attributes; proces...

Conceptual models

Asked By: IT learner | Asked On: Dec 27th, 2007

What are conceptual mdels

Answered by: jay_yasho on: Mar 31st, 2009

A conceptual ER model show how the business world sees the information. It shows only critical details in order to emphasize business rules and user objects. ideally It  includes only significant...

Data options and parameters

Asked By: alicaborys | Asked On: Feb 11th, 2009

What is the distinction between data options and parameters?

Answered by: seethala_goutham on: Jun 11th, 2009

data options means it sends the data in diff forms and where as parameters supports the data which sends through it

Match the following in the context of data flow diagram : i. Circle a. Source of data ii. Square b. File or data base iii. Arrow c. Conversion process iv. Parallel line d. Data...

Asked By: Rujul | Asked On: Mar 9th, 2007

Answered by: anoosha kokkula on: Jul 2nd, 2009

Answer is 2
Circle - Conversion process
Square - Source of data

Arrow - Data flow
Parallel line - File or database

Answered by: SashaFroyland on: Mar 1st, 2008

None of the above (in my opinion).
A -> C -> D -> b

A) source, then data flows to C) where it's converted or transformed, then it flows to D) parallel where it's pipelined into the B) the database as both updates in inserts.

What is an artificial (derived) primary key? When should it be used?

Asked By: Interview Candidate | Asked On: Jul 21st, 2005

Answered by: mvg_mca on: Mar 12th, 2010

A derived key comes from a sequence. Usually it is used when a concatenated key becomes too cumbersome to use as a foreign key.

Answered by: geeksds on: Sep 18th, 2008

It is a system-assigned number that is unique for each row of data in a table.  It is used by database administrators to allocate rows of evenly and efficiently on data storage / servers. 

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