IGNOU Solved Assignments RDBMS Lab

Question 2: (a) What is normalisation and why we do it? Comment on statement: “redundancy is some times good”. What are the approaches to normalise a database? What are the advantages and disadvantages of normalisation?

Ans:

The aim of the database system is to reduce redundan of, meaning that Information si to stored only once string information several times leads to the waste of storage space and an Increase in the total size of the data stored the Advantage of Normal:

Zatin are as follows:

No data value should be duplicated in different row unnecessarily
A value must be specified for every attribute in a row.
Each relation should be self-contained. IN other words, if a row a relation is deleted, Important Information should not be accidentally lost.
When a row is added to a relation, other relation in the database should not be affected. The disadvantage of normalization could be the time taken in it and the expanse on it possible.

(b) Which functional dependencies are to be removed to achieve which normal form, explain for all normal forms up to 5NF?

Ans:

Functional dependencies are to be removed to achieve at 3rd normal form.

The 5 NF relations are the relations in table 1 and 2 together with relation table 3.

Vendor Supply
Vcode	Icode
V₁	I₁
V₂	I₂
V₃	I₃
V₄	I₄

(1)

Vendor Project
Vcode	Icode
V₁	P₁
V₂	P₂
V₃	P₃
V₄	P₄

(2)

Vendor Supply
Vcode	Icode
P₁	I₁
P₂	I₂
P₃	I₃
P₄	I₄

(3)