CS614 Assignment # 2 Solution Spring 2013

Data warehousing (CS614)
Assignment # 2
Total marks = 20
Deadline Date = 07-May-2013

Please carefully read the following instructions before attempting the assignment.

Rules for Marking
It should be clear that your assignment would not get any credit if:


The assignment is submitted after due date.
The submitted assignment does not open or file is corrupt.
The assignment is copied. Note that strict action would be taken if the submitted assignment is copied from any other student. Both students will be punished severely.


1) You should consult recommended books to clarify your concepts as handouts are not sufficient.
2) You are supposed to submit your assignment in .doc format. Any other formats like scan images, PDF, Zip, rar, bmp, docx etc will not be accepted
3) You are advised to upload your assignment at least two days before Due date.
4) This assignment file comprises of Two (2) pages.


Important Note:

Assignment comprises of 20 Marks. Note that no assignment will be accepted after due date via email in any case (whether it is the case of load shedding or emergency electric failure or internet malfunctioning etc.). Hence, refrain from uploading assignment in the last hour of the deadline, and try to upload Solutions at least 02 days before the deadline to avoid inconvenience later on.

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Reference:

Please refer to the same case study as in your previous Assignment No1.


Question: [Marks 20]

In Task no. 3 of Assignment no. 1, you denormalized all one-to-one and many-to-many relationships; in this assignment you will denormalize all one-to-many relationships by taking into account the same Air Ticket reservation system, in order to optimize it further.

So, de-normalize all one-to-many relationships (left after Task no. 3 in assignment no. 1) using Pre-joining technique.

The pre-joined tables should:
· Contain no redundant columns (matching join criteria columns)
· Contain only those columns absolutely necessary for the application to meet its processing needs
Note:

You need to show the database resulted from the previous assignment (after denormalization) and the resultant database after performing pre-join denormalization in this assignment.

What is denormalization?
In a relational database, denormalization is an approach to speeding up read performance (data retrieval) in which the administrator selectively adds back specific instances of redundant data after the data structure has been normalized. A denormalized database should not be confused with a database that has never been normalized.
During normalization, the database designer stores different but related types of data in separate logical tables called relations. When a query combines data from multiple tables into a single result table, it is called a join. Multiple joins in the same query can have a negative impact on performance. Introducing denormalization and adding back a small number of redundancies can be a useful for cutting down on the number of joins.
After data has been duplicated, the database designer must take into account how multiple instances of the data will be maintained. One way to denormalize a database is to allow the database management system (DBMS) to store redundant information on disk. This has the added benefit of ensuring the consistency of redundant copies. Another approach is to denormalize the actual logical data design, but this can quickly lead to inconsistent data. Rules called constraints can be used to specify how redundant copies of information are synchronized, but they increase the complexity of the database design and also run the risk of impacting write performance.


Pre-joining

The objective behind pre-joining is to identify frequent joins and append the corresponding tables
together in the physical data model. This technique is generally used when there is a one-to-
many relationship between two (or more) tables, such as the master-detail case when there are
header and detail tables in the logical data model. Typically, referential integrity is assumed from
the foreign key in one table (detail) to the primary key in the other table (header).
Additional space will be required, because information on the master table is stored once for each
detail record i.e. multiple times instead of just once as would be the case in a normalized design


In this assignment we have to DE-normalize all the one to many relationships.
Anyhow solution of 1st assignment has been updated in the LMS. please have a look on it for better understandings