BITS WILP Data Warehousing Quiz-2 2017-H2

BITS WILP Data Warehousing Quiz-2 2017-H2

Q1.

A1.

B, C are true, in Type-2 change of dimension tables for incorporating changes in the dimension, we add a new row.

With Type-2 change, previous records remain as they were and the changed / new incoming row is simply inserted as new.

This type of change does partition the history.

URL: http://codingtechlife.blogspot.in/2017/10/data-warehousing-quiz-2-bits-wilp-mtec.html

Answer: D

Q2.
In this technique of Data Loading, if primary key of incoming record matches with that of some already existing record, matching target is updated:

A2.


Q3.

A3.


Q4.

A4.
(D), adding percentages does not result in anything meaningful.

Q5.

A5.


A primary key 'Product_id' in dimension table 'Product' may appear multiple number of time in the central fact table as a foreign key.

Q6.

A6.


Q7.

A7.


Q8.

A8.

URL: https://www3.nd.edu/~rjohns15/cse40647.sp14/www/content/lectures/07%20-%20Data%20Transformation.pdf

From this page, it appears that ‘data reduction’ is a ‘data extraction’ task.

Data Reduction

• Do we need all the data?

• Data mining/analysis can take a very long time

• Computational complexity of algorithms

Data Reduction

• Sampling:  selecting a subset of the data objects to be analyzed.

• Feature selection:  selecting a subset of the features to be analyzed.

• Dimensionality reduction:  creating new features that are a combination of the old features.

…

Data Transformation Tasks:

L9-P1: from this, reduction is more of a data-extraction task.

Q9.

A9.

URL:  http://www.vertabelo.com/blog/technical-articles/data-warehouse-modeling-star-schema-vs-snowflake-schema

Answer: True

“The most obvious characteristic of the star schema is that dimension tables are not normalized.”

“Snowflake schema stores exactly the same data as the star schema. The fact table has the same dimensions as it does in the star schema example. The most important difference is that the dimension tables in the snowflake schema are normalized. Interestingly, the process of normalizing dimension tables is called snowflaking.”

Q10.

A10.

URL: http://www.sql-datatools.com/2015/07/Triggers-SQL-Server.html

“Triggers are stored programs, which are automatically executed or fired when some events occur on the table like insertion, deletion or updation of data. It is a database object which could be defined on the table, view, schema, or database with which the event is associated”.